For some, jacket BCs are more comfortable on the surface since they hold you fairly upright when inflated.  However, if you fully inflate the BC, it tends to squeeze some divers as the jacket airbladder fills up with air.  The squeeze varies so try it on first and fully inflate it!   Because of the tendency to support the diver in an upright position, jacket BCs tend to make a diver plow through the water in a slightly fin down position unless they pay careful attention to their trim.

Back inflated BCs offer the advantage that when fully inflated the diver is not squeezed since the bladder does not wrap around the divers sides.  The disadvantage is that they tend to push the diver face down when fully inflated on the surface.  In this case the diver usually finds the minimum amount of air needed to hold themselves on the surface without being pushed face down.  A great advantage of back inflated BCs is their tendency to hold you level under the water and in good trim.

BCs come with differing sizes of air bladders, giving a BC a "lift" capability measured in "pounds of lift".  A range 22 to 75 pounds of lift is not unusual and shows that divers have lift needs specific to their type of diving.  Cold water divers wearing thick wetsuits (2 piece 7 mm) for example, must wear in the neighborhood of 25 or more pounds of lead to become neutrally buoyant on the surface.  At depth, the suit is squeezed and can become as thin as 30% of its original thickness, thus loosing its buoyancy.  If the buoyancy shift is 15 or 20 pounds, this means that a diver must have a BC that can be inflated to at least 15 - 20 pounds of lift to become neutrally buoyant on the bottom.  Warm water divers wearing little exposure protection have less buoyancy change at depth and can use a BC with less lift.

Finally, BCs are being made with shapes and strap locations just for women.  This can be a real plus for women who cannot find a good fit in a standard, unisex BC.