while floating on the surface the back inflate will push your face down, so you need to keep fighting for vertical balance, the vest will provide more vertical and balanced floatation.
So you should question yourself: if you are going to spend time on the surface (vertical)...or below the surface (horizontal).
I, as a dive master sometimes have to assist divers on the surface, so I use the vest style.
Eco Sonora
Absolutely no issue floating vertical or horizontal front and back with BP/W.