Just my two cents......I have a triple and rarely use more than the same 5 gear combinations. You need a granny gear or two, and some good spinning gears. I shift way less than I ever did on my 2 wheelers. Maybe that's because trikes are just slower, period. Unless you're going to be climbing huge hills - and you'll probably end up putting a motor on it, anyway. Go for the one that feel the best to you when riding, has the best service/parts capability. You can change cassettes if you need to adjust gear range, but a double is plenty.