How you float at the surface depends on the balance between where your lift is, and where your weight is. In a back inflate or backplate system, the lift is all behind you . . . but a lot of us are diving steel tanks, so we have something behind us that seriously wants to sink, and it all balances out. In addition, backplate systems use a crotch strap to prevent the bladder from riding up on your back at the surface, which further decreases the tendency to tip forward.
I've been diving a back inflate or a backplate since I got certified, and I have never, ever, in any exposure protection and tank combination, experienced the gear pushing me face down in the water.
What kind of BC you buy is really a very personal choice. There are a few basic things to consider: It has to FIT. And by fit, I mean it has to be able to cinch down around you enough to keep that tank on your back in a stable position. It is my opinion that this is much easier with a BC that includes some kind of rigid plate in its construction, whether that is plastic and part of the BC, or metal and a component of a system. My husband's SeaQuest Balance, which he really likes, has a plastic plate as part of its design.
Fit can be hard to assess in the shop, because putting the BC on and walking around with it, with no tank and no exposure protection, doesn't give you a very good idea of how it will work when you actually dive it. Sometimes it's pretty easy to adjust something with bare hands, and with no weight hanging off the back of it, but much more difficult to get the straps tightened enough when you have cold hands (or gloves) and 35 pounds of tank on your back.
The second thing is comfort. Some people like the feeling of the BC wrapping around them. Others, like me, find that irritating. I like having as little as possible on the front of me -- this is the design of back inflate and backplate systems. I've also found that Velcro fatigues quickly on dive gear, so I don't like any BC that depends on a Velcro cummerbund for stability.
If you are going to opt for a BC with pockets, make sure the pockets are easy to access using the exposure protection you will need. If you have to wear thick gloves, it may be difficult to get to the zipper and get it open. Some pockets are virtually unusable underwater -- you can't see them, and with thick gloves, you can't feel the zipper pulls, either.
Another aspect of a BC to consider is how you will carry your weights. Many BCs have integrated weight systems. If this attracts you, assess how they work -- how securely are the weights held, and how easily can they be removed (realizing, of course, that the two things are fundamentally incompatible!) Also find out if the BC has trim pockets (small pockets in the back that will accept additional weights) and if so, look at WHERE the trim pockets are. If you need to distribute some weight to get yourself horizontal in the water, you may need to put some weight up on your back, and if the trim pockets are at waist height, they aren't very useful.
I'm a backplate person, myself -- I find it hard to resist a system that's entirely modular, completely adjustable, reduces the total ballast I have to carry, improves my horizontal balance, and leaves the whole front of me free. BUT . . . I have to wear a weight belt (I don't mind) and I have to have pockets on my exposure protection (which I also don't mind), and both added to the cost.
The best thing about a backplate system? It makes mounting a canister light easy!
