Wow, what a lot of hot air.
To answer your initial question Beppe, on what kind of BC to buy:
I laugh constantly at the amount of equipment the average American diver buys and uses. I agree wholly with your use of EAN to help off-gas, I myself can run five dives per day for several weeks and dream of using EAN (kind of hard to get O2 in the outIslands) so that I stop sounding like popcorn. However, it really doesnt mean that you need to load up on reels, liftbags, H-valves etc. If you are worried about being visible on the surface, carry a surface-marker buoy - I do. If you are not cave/wreck diving, why carry a reel? In the end, unless you are a commercial or penetration diver, you do not need to carry all of that equipment. Thus to the BCD.
Back-inflating BCDs were designed originally for commercial divers. They are designed a>to carry all of that equipment, and b> to allow more movement with all of that equipment. They have become very useful for tec divers for that same reason.
Many Americans wear these BCDs, and all of the equipment because they think it makes them look experienced and competent. Really all they have done is fall for salesmanship at their diveshop. I took on some referral students a few years ago decked out in OMS, head to foot - dual-bladder, the works. Why had they bought this gear? Their initial instructor sold it to them, and laughed all the way to the bank with his commission. At the end of the day, look to what the pros wear.
Stan Waterman: Scubapro Classic
Howard and Michelle Hall: Scubapro Classic
The Taylors: Scubapro Classic
Jef Fox: Scubapro Classic
Genie Clark: Scubapro Classic
Basic, durable and reliable. No back-inflator, no steel plates, no d-rings.
Usually you can spot the good, experienced divers by the lack of equipment.