Well i was in your situation not so long ago, and the best advice and im sure many will support me on this is to go out and rent more bcd's until you fall in love with one. Dont go purchasing the first one you fall in love with though!
Im not an expert but from my research i think these are the pros/cons of each:
Jacket:
Pros: Upright in surface, most commonly used, you can easily tell its inflated
Cons: squeezes you in, too much space used and cramping
Back Inflation:
Pros: Able to move more freely, nothing in front to limit your movement. Better horizontal position in water
Cons: Might push you downwards (face-first) on surface.
BP/W
Pros: Able to move freely, nothing to limit movement, better horizontal position, more streamline, easily configured and adjusted
Cons: Someone else pitch in
I havent tried a back inflation, but by the description of BP/W setups, i simply fell in love with it and have placed my order. But if your not as risky as i am, i say go out and try the different types.
Good Luck and Dive Safe!
Moh