Cruise critic will tell you a lot, but I find the crowd there is a different flavor than here. I'd check it out but take comments with a grain of salt. Sometimes you can tell, like other travel sights, from the kind of criticism whether it's something you would worry about or not. For me, who only travels with a carry-on bag, the size of the closet - as an example - isn't going to be an issue.
One thing I have used cruise critic for is to see options at different ports. Most people there take the ships tours. I avoid those like the plague. I've found that anything listed as a ship tour will be available, cheaper and better, by either doing it on your own or booking a local tour directly. In Cozumel, I booked a two dive day online with a guide, boat and their equipment. The price was less than half the cruise lines guided two dive package. I walked from the ship to the dive shop. After waiting awhile for a large group, who didn't show, we ended up going out on the boat, with the guide and boat driver, by myself - I could choose anywhere I wanted to dive.
I've been on four or five cruises, I'd have to think about which. Each time I've booked through vacationstogo.com. They are an online travel agent. Their prices are the same as all the other online agents, generally a lot cheaper than what you find on the cruise line sites. I like their search engine better than anywhere else I've tried. The cruises I booked were all done correctly with no unexpected headaches, so I have no complaints with them.
On their search engine you can find information about the ship, amenities, photos of cabins, deck plans, etc. to help you decide on what works for you. They have a star rating for each individual ships, when it was built, when it was last updated, etc.