halemanō;5982166:If one is hoping to "easily" teach new divers about controlling their body position under water the differences in design between back inflate BC's and vest BC's do make some things easier and some things harder.
"'Easily' teach" implies that it is easy on the instructor, not necessarily the student.
There is SO much an OW student learns during during OW, I would be surprised if the slight differences in ease of instruction or ease of learning would make much of a difference to the student. They are saturated with new information and they are very green. The differences between the two configurations become increasingly noticeable once you have an understanding of buoyancy and trim, not necessarily when you are learning what they are. The student understands buoyancy control and trim as he achieves control, and the ease in which he gains that control is the issue. Personally, having dove both configurations when I was a new student, I found the BP/W easier on trim and more difficult on buoyancy (more a factor of over-weighting, had I been properly weighted I suspect there would not have been a difference.)
I appreciate your water-skiing analogy, though I don't feel learning in a BP/W is more difficult than a traditional vest.. there's not a substantial initial toil. Here, it is not hard to find a shop that uses primarily back-inflate, and there are even shops that rent primarily BP/Ws. The instructors I know that teach from the BP/W shops are excellent. If a student has their own gear and are not in a shop BP/W, they teach them in what they have, though I sometimes hear some frustration as those tend to be the students that struggle with things that the instructor may feel could be fixed with a BP/W. And if the student tries the BP/W, they usually make the switch because they find it easier.
Your point about the "skiing around the boat" is well taken. In North and Central Florida, if a student becomes an active diver and has the desire (which is a minority, but there is a substantial population here given the proximity to cave country) they may progress rather quickly into overhead environments, more a factor of water temperature than anything else. It's where you dive in the winter. That might not be a good thing. And learning in the "wrong" gear for that environment might slow a student down as they make the switch, or might get them killed in a cloud of silt at the bottom of a supposedly OW friendly cavern. I can think of 2 that are regularly dove by OW divers that, at 100 ft at the bottom of the line, have a pretty soft bottom and access to a cave. One is a very popular OW training site. OW divers have died at both. The again, learning or diving a BP/W doesn't make those environments any safer either, and may give the student a false sense of security, so really it's a whole separate issue. But if they live in an area where it matters, learning good trim (which is easier in a BP/W) and finning techniques early will make them safer divers.
