Back inflation can tip you forward... you need to make sure you compensate correctly for it so it doesn't happen. If I have only an aluminum 80, I usually have to position my weight belt "just right". It is way easy with a steel tank, and there is no compensation needed.
My NAUI ITC did not reccomend one type of BC over another... some just suggested that you have the same type of BC that your students will have. However, my Chute2 is a back inflate, and I really have no problems teaching students who are wearing a vest style.
As for rescue... the BP and wings ARE harder to remove. No doubt about it. Fortunately, usually by the time a person has progressed to diving with a BP and wings, they are not a likely candidate for rescue. Albeit much maligned by many who prefer a BP and wings, quick releases make removing most BCs a breeze. I have yet to see a QR fail in the water, so I am not one to "dis" their reliability. Still, if the divers you hang with use BP and wings, then you should practice rescue with THAT type of gear.
Personally, I try to make as few waves as possible with my gear configuration whenever I take a class (my odd humor gets me in enough trouble as it is). My ITC did not seem to like DIN and steel 120s so I switched over to a yoke and an AL80... I still keep that set-up for the pool. As much as I do NOT see a problem with the "bungeed wings of death", my cavern/cave instructor to be sees them as anathema. OK, I bought another "unbungeed" set of OMS wings to appease my instructor. It's usually easier to swim with the current... stop trying to fight it!
