Most people choose a cruise based on its itinerary, but after 22 cruises and hundreds of conversations with travelers, I am here to tell you that the size of the ship could very well be more important than where you sail. Though you probably wouldn’t think so, ship size can actually determine a surprising variety of cruise experiences—ranging from what you’ll be able to see and do in ports of call to what you’ll eat on board and how rested you’ll feel by the end of the trip. In fact, a vessel’s most vital statistic is the number of passengers it carries. Here’s how to choose the best ship every time:

Choose a small ship (fewer than 300 passengers) when…

Your goal is to explore off-the-beaten-path places.

Big ships have to dock at big—usually industrial—piers; small ships can access small, charming ports, and they tend to stay longer and dock closer to town, giving you more time to explore. There are no crowds to beat, so you can see places at their most pleasant and authentic. When my husband and I sailed on Windstar Cruises’ 148-passenger Wind Star to Mediterranean islands that we might otherwise never get to—Cephalonia, Corsica, Elba, and the like—we stepped off the ship into fishing villages where we could rent a bike or car right at the pier and take off on our own.

We were the only Americans on the beaches and at the tavernas. A small ship can also turn a been-there-done-that part of the world into a new frontier: When you’re on a ship like the 208-passenger Seabourn Pride sailing in the British Virgin Islands or the Grenadines, you see an entirely different Caribbean than when you’re on a megaship sailing to St. Thomas or Cozumel.

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You want that sense of being on the sea.

The bigger the ship, the less you see and hear the water; on a 4,000-passenger floating theme park, it’s easy to forget you’re not on land. The smaller the vessel, the more you feel the poetry of the ocean—its vastness, its power—and the more likely you’ll be allowed to hang out on the bridge with the captain and crew, as is the case on Windstar, Star Clippers, and the Sea Cloud ships. The downside? You might feel a few too many waves.

You can do without a lot of living space.

Cabins are usually compact (say, 150 to 200 square feet), and balconies and floor-to-ceiling windows are rare, though you can find them on the newest small ships—or the largest, such as the 296-passenger Silver Cloud or Silver Wind.

You don’t need to swim laps or hit the treadmill.

If there’s a pool on a small ship, it’s tiny; if there’s a fitness center, it’s sparsely equipped. The upside? You feel like you’re on a boat, not at a megaresort, and if you’re on deck and you forgot your camera or your binoculars, your room is only 30 seconds away, as opposed to a 10-minute trek. Even when there’s no pool, there’s usually a hot tub or two.

You want to travel with like-minded people.

Everybody on a small ship has one important thing in common that binds them: They’ve picked that ship because they want to explore unusual places. Often, they also have common characteristics based on the ship chosen. On Windstar, for instance, people are relatively young and energetic. Why? “If you want to sail with younger people,” the ship’s doctor told me, “choose a ship with no elevator.” On Grand Circle’s 50-passenger Arethusa, where local guides well versed in the region’s culture and history sail with the ship, you’ll find intellectually curious and extraordinarily well-traveled retirees, many of them former teachers and professors.

You’re in a mood to be social.

Forget anonymity. On a small ship people get to know one another quickly, and the staff learn your name—and your favorite drink—in no time.

Choose a medium-size ship (300 to 1,300 passengers) when…

Your goal is a mix of sightseeing and pampered relaxation.

Medium-size ships tend to spend more days at sea than small ships do—which means more lounging by the pool, going to the spa, and time for onboard classes (from wine-tasting to photography). Still, midsize ships have more time in port than large ships do. Crystal Cruises’ ships, rated number one by Condé Nast Traveler readers, will spend 25 percent more days in port this year than last. Azamara Club Cruises may be the midsize line that has the most evenings in port.

When I sailed the Adriatic coast on the Azamara Quest, we hit a new port every day and stayed in most till 11 p.m., allowing us to sightsee at a leisurely pace and experience the local nightlife. After 6 p.m., the heat subsides, the light is better for photographs, and the locals leave the beach and come into the Old Town to play.

You like some scheduled activities but not too many.

On big ships, just reading the daily program of trivia contests, fitness “seminars,” and scavenger hunts can be exhausting. Midsize vessels offer programs that are more enriching, enabling you to leave the ship with new knowledge or a new skill. Oceania’s Marina and Riviera, for instance, focus on cooking and wine-tasting classes—there’s a dedicated Bon Appétit culinary center on each—while on Crystal, instructors from the University of Southern California teach moviemaking on your iPad and magicians from Hollywood’s renowned Magic Castle share secrets of their trade.

You want a private balcony.

Most small ships have few, if any, balconies. Large ships have plenty, but often they aren’t very private. Midsize ships, on the other hand, tend to have the most balconies that are both spacious and private enough for two people to enjoy breakfast in their bathrobes. My balcony over the stern on Regent Seven Seas’ Mariner was so huge—yielding 270-degree views of icebergs calving and crashing into the sea off southernmost Chile—that I was reluctant to leave it for fear of missing something. Indeed, we ate many a meal on that balcony. Why peel ourselves away when room service can be ordered from the main dining room menu, is served course by course, and costs nothing?

You want a choice of good restaurants.

Most small ships have only one or two dining options; large ships have plenty of choices, but the food is usually mediocre unless you pay a $25-per-person (or more) surcharge to eat in the better restaurants. Increasingly, it’s midsize ships that cater to foodies because they’re big enough to offer a variety of restaurants yet small enough to provide fine cuisine. Oceania Cruises’ 1,258-passenger Marina, for instance, has four first-rate specialty restaurants, including a French one created by Jacques Pépin. Seabourn Odyssey has six dining choices for just 450 passengers.

You dislike assigned dinner seatings and times.

On some small ships—especially river ships—I’ve had to have every meal at a specific hour and at a shared table, and on some megaships, I’ve ended up eating every dinner at the buffet because the assigned dinner seating was inconvenient and getting a reservation for an alternate time proved too tough. Midsize ships, by contrast, generally make it easy to dine when—and with whom—you want, but the larger the ship, the more likely it is that you’ll need to reserve tables.

You want to socialize with some people but avoid others.

On a midsize ship, there are enough hideouts that you can be anonymous when you want to be.

You hate feeling nickel-and-dimed.

Many travelers choose midsize ships because they dislike the megaships’ litany of extra charges—for certain restaurants, beverages, and activities. When comparison shopping among midsize ships, don’t forget that Regent Seven Seas’ fares are the most all-inclusive, covering even most shore excursions, fine wines and premium spirits, all minibar items, and gratuities.

Choose a large ship (1,300-plus passengers) when…

Your goal is vacation—not travel.

If you board a large ship hoping to absorb a foreign culture, you will likely be disappointed. Time ashore is relatively short: You can end up with only a few hours in a city you’ve traveled thousands of miles to visit, and you don’t get to see it in the evening—which means you’ll miss a big slice of the local scene. But I choose these ships for my own family vacations because they’re affordable and I can sit on my balcony for a week staring at the sea and reading novels while the kids’ club exhausts my children for me—for free—and allows me seven “date nights” with my husband. As a bonus, we get a quick taste of a new place every day and a room with an ever-changing view—all for a lot less than what a land resort would cost.

You’re worried about mal de mer.

The bigger the ship, the less motion you feel.

You’re taking the kids.

While a few midsize ships (Crystal’s and Regent Seven Seas’) run children’s programs during school holidays, only large ships have elaborate—and complimentary—child-care centers and
affordable family suites. Disney Cruise Line has the most comprehensive child care of all, with a nursery for tots starting at three months and a kids’ club that can take your children off your hands from 9 a.m. till 1 .a.m. If you can’t stomach a megaship, your best bet among midsize lines is likely Crystal, the only luxury line with children’s clubhouse facilities.

You’re up for exercise.

It’s a workout just to walk from one end of the ship to the other, not to mention from the gangway to the port entrance. (Forget something essential in your room and you could have a 15-minute jog on your hands.) On large ships you also get a basketball court, a tennis court, a track, a huge gym, and much more. Royal Caribbean’s ships are the most sports-oriented of all. On Navigator of the Seas, we never encountered a wait or a charge for any of the activities—which included rock climbing and in-line skating.

Nightlife is critical.

Only on large ships will you find multiple bars, shows, dance lounges, comedians, a big casino, and other late-night entertainment options. If fine dining is important to you, Celebrity Cruises’ newest ships, Reflection and Silhouette, have ten dining venues each and probably the highest caliber of cuisine, although many of the specialty restaurants tack on a fee of $25 or more per person.

You’ve got a troupe of travel companions with conflicting needs.

Calling all multi-generational families: With the range of activities and amenities on offer, a large ship makes it easy for everyone to be together when they want, apart when they prefer, and content most of the time. I’ve had two successful family reunions aboard Holland America Line, whose ships are sophisticated and sedate enough for adults, kid-friendly enough for hyperkinetic children, and small enough for mobility-challenged grandparents.

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