Excerpts from an MSNBC Article.

Princess Cruises
Best Ships: Crown Princess, Emerald Princess

Why: While we like any of Princess' Grand Class vessels for their blend of big ship options and small ship cozy, Crown Princess and Emerald Princess, the fleet's newest, offer some first-time-ever features.
Stay here: Both boast the line's traditionally high percentage of suites and mini-suites (which means booking a bigger cabin may not be too much of a splurge). The "piece de resistance" is the Grand Suite, which features separate sitting area, balcony that stretches between living room and bedroom, and a fabulous whirlpool tub. But even the standard mini-suite is charming and comfortable.
Out on deck: What could be more romantic than a night at "Movies Under the Stars," a retro drive-in where you recline on padded loungers (you can snuggle under the wool tartan blankets)? During the day we love The Sanctuary. A completely new invention, The Sanctuary is a (mostly) shaded Zen-like retreat, complete with waiter service, spa menu and massage services (a couples' massage is available).
Indoor romance: Check out the spa's couple's Rasul room (it's a mud room with steam — and it's more fun than it sounds!). Adagio, a new concept lounge featuring a cabaret singer, is lovely and private — way up on one of the top decks.
Dining: Open-seating (as well as traditional) dining is available. But the most romantic option — and unique to cruising — is the Ultimate Balcony Dining dinner experience. For $100 per couple, cruisers are treated to a lobster dinner with champagne and course-by-course service. Only caveat: Your cabin must have a balcony. We also love the ship's two specialty restaurants. Request a banquette at Crown Grill, a steak and seafood restaurant with an open grill; Sabatini's, the line's Italian eatery, should not be missed. Another favorite is Vines, the ship's wine and sushi bar.
Downside? While the ship's deluxe mini-suites are lovely and comfortable, the all-open-air balconies (applies to any cabin on Dolphin deck) are anything but private.
Special events: All of the Grand class ships are premier options for onboard weddings. Both have dedicated wedding chapels and captains empowered to perform ceremonies — and friends at home can watch live via Web cams!.

Crystal Cruises
Best ship: Crystal Serenity

Why: In general, Crystal is the best choice for folks who want big-ship features and small-ship luxury. In particular, while this newer ship offers many of the same features as Crystal Symphony does, the penthouse suites, the most romantic accommodations, are more plentiful.
Stay here: The aforementioned penthouse suites, which come in three categories. All have verandahs, butler service and marble baths with Jacuzzi tubs (not to mention state-of-the-art tech toys), and are roomy enough for in-room massages. Another plus? Passengers in these staterooms can order off the menu from Crystal Serenity's fabulous specialty restaurants.
Out on deck: Head for any of the terraced decks on the back of the ship.

Indoor romance: Head for a private corner of the Sunset Bar (at the forward end of the Palm Court) — it's a great spot for sunset-watching. We also love the clubby-pubby Avenue Saloon.
Dining: Try any (or all) of Crystal Serenity's specialty restaurants, such as the Northern Italian Prego and the Asian Silk Road. Or indulge in course-by-course room service on your verandah.
Downside: Crystal still maintains a set-time, assigned-tablemates scheme in its main dining rooms.
Special events: No weddings but the ship does offer vow renewals.

Norwegian Cruise Line
Best ships: Norwegian Jade, Norwegian Jewel, Norwegian Pearl
Why: First and foremost, NCL's "Freestyle Dining" philosophy (passengers can dine without the hassle of assigned times and tablemates at a variety of restaurants) is perfectly suited to table-for-two travelers. A close second are the ships' Courtyard Villas. The relatively new concept (and, as such, only found on NCL's newest ships) is aimed at creating a small, boutique-style hotel within the framework of a larger resort. The villas are located away from the so-called fray — and offer a host of special perks, from access to a fabulous Asian-inspired pool area (complete with Balinese bed and hot tub) to suite-holders-only breakfast and lunch at Cagney's.
Stay here: The aforementioned Courtyard Villas feature separate living and sleeping rooms (there's the master bedroom and also a smaller, window-less room with bunks), flat-screen television, butler service and, the best part: a swishy bathroom whose whirlpool tub is set into a picture window alcove.
Indoor romance: Try dinner at Cagney's, the ship's steakhouse and Le Bistro, a French eatery; for drinks, the Star Bar (Norwegian Jade) and the Plantation Club (Norwegian Jewel) are tops.
Onshore: Itinerary-wise, Norwegian Pearl, with its romantic spring and summer Alaska sailings, wins by a nose over its fleetmates' Europe and Caribbean routes.

Carnival Cruise Line
Best ships: Spirit-class vessels, including Carnival Pride, Carnival Legend and Carnival Miracle
Why: At 88,500 tons and with 2,124 passenger capacities, these ships are big enough to offer plenty of onboard variety — but not so huge that they feel impersonal. Plus, because these ships have a high balcony ratio, it's easy — and not at all expensive — to nab a cabin with your own verandah. The ships are, for the exuberantly-designed Carnival, the fleet's most elegant, featuring an Art Deco scheme.
Stay here: If you're splurging, the "penthouse suite" comes with a huge balcony and elaborate bathroom. The more affordable standard verandah cabins are pleasant, though.
Out on deck: Go forward on Atlantic deck to the enclosed portion of the ship's exterior promenade.
Indoor romance: Try a couples' massage at Spa Carnival. The foyer lounge and the cigar bar are the most intimate drink spots.
Dining: Bypass Carnival's assigned dining scheme at its main restaurants and head to the Spirit-class ships' reservations-only supper clubs.
Special events: Spirit-class ships have wedding chapels (though captains are not allowed to perform ceremonies), and staffers will help arrange weddings and vow renewals.

Read the entire Article: http://www.msnbc.msn.com/id/24935337/page/1/