The person wanting equipment advice is asking about warm water type BCDs. The BCDs they ask for advice on - are not meant for cold water diving really and I very much doubt they'll be wearing more than 5mm wetsuit in the Red Sea.
By saying you have a negligible amount of air in your BCD when underwater, is correct. To counteract the compression of a 5mm full wetsuit in moderate temperatures you really don't need much air in there at all. A major function of a BCD is to give you boyancy on the surface and many back inflating BCDs mean that you have to counteract being pushed fowards, and quite frankly, in my opinion don't add any benefits at all for the recreational diver.
Also - I am trying to give someone advice about BCDs involving - function, comfort and price. I didn't say that only prices matter. For functionality and comfort and price I would say the scuba pro glide wins over any sea quest back inflating BCD and I said why. Price does matter for some of us who aren't loaded.
I never said back inflation BCDs push your face right into the water either - I said they "push you forwards"
Also, the glide 2000 comes in small, meduim, and large - and it is very adjustable. It WILL fit anyone, unless they are overly large in which case they should not be diving!!
Most of the worlds waters are cold - correct but most diving takes place in the warm waters. The greatest amount of marine fauna exists there and that is the major attraction for most divers. So lets forget BCDs for cold water diving for now. That's not what this diver what to know about.
It is cheaper to re arrange your weights (maybe add some to your ankles etc.) to get a better trim than to purchase a back inflation BCD. Through my research into dive gear - I've found that back inflation doesn't add much functionality and for the extra price, it's simply not worth it, especially when there are a wide range of excellent BCDs out there.
That said - I'm off home to fetch my BCD and get into the water to watch the coral spawn
bdaskink.