Like aRea said, each is very different, and even among the largest island, Roatan- due to it's size, the choices there can mirror each of the other islands, as well.
I looked at your dive profile. You've seen Curacao, Belize and Cozumel- at least in terms of warmwaterprettyfish type of places.
Utila is, overall, a look at Island life in the 1970's, with the added mix of the information age being available at every turn. If you want to see it, go see it now, it is in the process of being colonized very quickly. Any number of excellent dive ops, a few restaurants with notable local flavor, and any number of small bars. Not a pretty town by any standard, and most of the tourist life is somehow laced into it's confines. Transportation is a minor issue- you can not simply fly from the US and pop out of the plane in paradise. Check other posts for these considerations of utilizing ferry, small plane, or sailboat to make your arrival after flying to Roatan or the mainland of Honduras.
Gunaja is a very remote portion of the chain of the Bay Islands and as such, the connections issues as mentioned above for Utila are very much-so magnified. Dunbar Rock as pictured above is one of very few AI resorts available, the others are on the main portion of the island of Guanaja. Development is a long way down the road for Guanaja, but you will find the main population center to be concentrated on a settlement of patchwork concrete and wooden walkways surrounded by buildings on stilts- also located South off of the main island. This is the only real option for "restaurants" as you mentioned, but I think that would dissolve as a concern, passing more the status of an amusing afternoon visit, after spending a week diving at an isolated tropical resort setting. I am very familiar with the Island and it's diving itself, but I am not well up-to-date on currently existing dive ops and names.
Roatan is indeed the most developed of all the islands, but "privacy" is still available in all forms, even though you can get direct flights from a few US cities. It is a long, narrow island that allows for dramatically different terrestrial and diving experiences. The greatest volume of travel visitors frequent what is sometimes generically called the West End~ this is a great center for restaurants, small rustic bars and a beach. This, in reality, also includes the West Bay area, as well as the several AI resorts (AKR, IoLR) that curve from there and dot the near North Side. The West End area is largely served by day-dive opertaions (CCTD, Banarama, HalfMNoon, etc) and guest houses. Along the South shore are three AI's (BKK, FIBR, CCV), and further East is a good AI (RHR) as remote as anything you might find in Guanaja.
Of the three, I prefer the diving along the shallow, Sunlit walls of the South Shore of Roatan. It holds the most diverse selection of soft and hard Corals, and also serves as an incubator with numerous Juveniles of fish and Crustaceans.
If I were to pick ONLY one place to go, I would seriously consider Utila, as I said, before it gets ruined by success. You might want to see one of the last vestiges of Caribbean life before it is gone forever. Unfortunately, the same reasoning would apply to my favorite area of Roatan- it is such a delicate environment, that the changes underwater are dramatic from year to year.
Tough call.
