A friend of mine's family owned an older Gemini for many years... and cruised from the Great Lakes down to the Caribbean for many years on theirs.
The Gemini is a pretty solid boat for a reasonable price, and provides a lot more living space than a monohull of comparable size, but is a bit more sensitive to weight, so you can't load her up like the monohulls.
The beam on the Gemini is only 14', so she can fit in some of the larger slips, which can make finding dock space for her simpler than some of the larger cats, and about the same price as some of the larger monohull boats you're looking at, since a 40' slip will fit both a 38' monohull or a Gemini 105 Mc.
You should also join the Owner's Info Center at the Gemini website
. They have a good article about an Atlantic crossing made in one.
The shallow draft makes it an excellent choice for the areas you're looking to sail.
I can't really give you any specific information without knowing a bit more about what you're planning—how many people will be aboard, etc. The boat is a three-cabin layout with additional berths in the salon area.
The master cabin is the largest and has much more room than the smaller two cabins... but some people I know have found the aft cabins more comfortable while on a passage due to the reduced motion and noise of being aft, rather than forward.