At the time of this writing, the Nikon D7100 is the best cropped/Dx camera you can buy, with advanced features such as removal of the anti-aliasing filter, special 1.3x crop mode, and a 24Mp sensor. It is an excellent camera for travel and cruise photography, especially with it's 1.3x crop mode, as it allows more range without the need to carry more lenses.
Suitability for Travel: Rates a 4 out of 5. While image quality and flexibility are unsurpassed, DSLRs in general, even light weight ones are just a bit cumbersome to travel with. They often require dedicated camera bags, especially if you take a lot of extras; such as lenses and accessories.
What is an anti-aliasing filter? Sometimes called a low-pass filter, it reduces the chance of moiré patterns in the photo. Moiré is an artifact of the digital format, and shows up as parallel lines from anything having a repetitive pattern, such as threads in clothing. Nikon states that they have discovered a way around moiré with their high megapixel cameras. For that reason, they have removed the anti-aliasing filter normally used on their digital cameras. Lack of the filter results in a slightly sharper image.
The effectiveness of removing the anti-aliasing filter wast tested by photographing this scene with the D90 (which has an anti-aliasing filter) and the D7100 (that lacks the filter), and comparing an enlarged area of the photo for sharpness. The yellow box in the lower right is the cropped area for each photo shown below. Both cameras used the same Sigma 17-50mm f/2.8 lens.
Clearly the D7100 has a sharper photo. While there may be additional reasons for the difference, the anti-aliasing filter is a big part of the reason.
The D7100 also includes a 1.3x crop mode. While this at first seemed to be somewhat of a gimmick, in practice it works really well. This additional crop mode provides a total effective crop facor of 2x (vs. full frame), and it provides a bit additional reach for those times when it is needed. The camera's normal resolution is 24.1 Megapixels, and when in 1.3x crop mode, the resolution is still at 16 Megapixels. And given that the pixel pitch (size of individual pixels) is unchanged, there should be no loss of quality.
Shutter Lag: While some are aware compact cameras have shutter lag, not many realize DSLRs can suffer from this as well. Shutter lag is defined as the time lapse between depressing the shutter button and the photo being taken. The longer the shutter lag, the less desireable - especially for sports and action photography.
Shutter lag is typically a function of the focusing mechanism, buffer, and sophistication of the electronics package. When comparing cameras, it is useful to compare three shutter lag values; manual focus, AF-C (continuous focus), and Live View.
The above table shows tested shutter lags (www.image-resource.com) of several popular DSLRs. From this table you should see that there is a clear advantage of advanced and professional vs. entry-level DSLRs. And you should also see that you take a huge performance hit when using live view. For this reason, live view should never be used for sports or action photography (unless shooting video).
Of one concern is DSLRs having a 0.25sec or longer shutter lag - especially in AF-C mode. The best compact cameras are in this range, and I would expect better performance out of even entry-level DSLRs. If sports and action photography are a significant need for you, the lower this lag is the better.
Given that a 90 mph fastball travels 13ft in 0.1sec, you should see that shutter lags even in the 0.2 sec range can be problematic for sports and action photography. For cameras with slower shutter lags, often the only solution is to use the camera in continuous (burst) shooting mode.
Summary: You choice of the camera you wish to use is as much a matter of your pocket book than anything else. A good photograph can be taken with an inexpensive camera, and a lousy photo can be taken with an expensive camera. For some folks just starting out, the entry-level D3xxx presents tremendous value, and there is an in-camera help system that may prove to be indispensible. The entry-level cameras are often light weight, easier to setup and use, and if they are lost or stolen, its not as expensive.
Often its better to have a camera that is easy to use as you can concentrate on taking the photo rather than setting the camera up. However, the chief advantage of the more expensive camera is flexibility, and the ability to operate in the fringe environment (low light, dusty or wet conditions, and so on).
Remember the theme of this review is the selection of a camera that you may want to take with you on a cruise. If you don't want to lug a heavy, super-expensive pro camera with you, cameras in the D3xxx to D7xxx range will provide satisfactory performance in the cruise ship setting, yet not be too heavy to carry.