Hi Wazoozaw,
We now live in Roatan & have spent the last 3 years exploring Central America including El Salvador, Nicaragua, Costa Rica, Panama, Providencia & San Andres, and now Honduras & Belize. The rainy season in all those countries extends into November, sometimes December or January, & the amount of rain and thunderstorms on the mainland, including Belize, is much higher than in the islands offshore, including the Bay Islands and Providencia/San Andres. The hurricane season in the Caribbean officially lasts from June through Nov, however in the Western Caribbean the peak season is Sept & Oct.
Belize gets far more tropical storm & hurricane activity than the Bay Islands due to Cape Gracias Del Dios acting as a major obstacle to normal hurricane tracks heading for the Bay Islands. For example, last year in Aug Tropical Storm Ernesto was headed towards the Bay Islands but once it got 100 miles off the Cape it turned north for 2 days and then back west, missing Roatan by over 150 miles and slamming directly into Belize & the southern Yucatan. This is a typical storm track for this area, in order for a major storm to hit Roatan it must come across the mainland, which is extremely rare. Ernesto was the only storm to come even close to the Bay Islands last year & so far this year we've had nothing but great weather. If you take a look at the NOAA statistics since 1970 you will see that over the last 43 years Roatan has only been significantly affected by tropical storms/hurricanes 3 times, whereas Belize is much higher.
As far as diving is concerned, like many places you have to know where to go to get the best diving. The diving on the south shore & east end of Roatan is much better than in the West End/West Bay area in our opinion, and we do liveaboard charters in all of the Bay Islands including Roatan, Cayos Cochinos, etc. It is correct that there is not much in the way of large marine life, this is not where you come to see that. However, statements that there are no fish must be coming from divers that simply weren't taken to the right sites. We were diving just 2 days ago right off French Cay Harbor & the fish life was incredible, at times totally surrounding us. The whale sharks are here right now & have been sighted daily off both the south & north shores & Utila has even more of them than Roatan. Unfortunately they won't be here in Oct, wrong time of year. The above comments about diving equally apply to Belize, particularly in the outer atolls such as Lighthouse & Glover reefs, absolutely outstanding diving there too.
As far as the reefs go, the coral off the south shore of Roatan is outstanding, dramatic walls full of color that plunge from 30 feet to over 140, with overhangs, swim throughs, canyons and chimneys. Roatan's reputation is built on the vibrancy of its coral reefs & they are the main reason divers come here, but again you need to get off the beaten track where most divers go. It's also important to go to dive sites at the right time of day, in general you want mornings on the south side & afternoons on the north, no light equals no color. If you would like to see some examples take a look at the photos on our Facebook page, we are far from professional photographers but they will give you an idea of what we dive in daily.
Finally, with regard to cost there are few places in Central America or the Caribbean where the diving is as affordable as the Bay Islands. From what I have seen, Roatan & Utila have the lowest cost per dive and the least expensive courses anywhere in the Caribbean, and possibly all of North & Central America. You would be here in off season & should be able to find great deals on accommodation & diving packages. Roatan has accommodation to fit all budgets, ranging from backpacker hostels to high end hotels with everything in between. It also has a huge variety of things to do on shore when you're not diving. A great place to look for deals & info about Roatan & Utila dive shops, hotels etc is actually on Facebook, many of the resorts & dive operators, especially the smaller ones, primarily use Facebook to communicate and do not keep their websites very current. The Facebook pages however are often current right up to that day.
Good luck with your search!