I tried a BP/wing during my DIR-F course. I was not impressed. It was a pain to adjust, never did get it to where it was comfortable on land (with a 2pc 5mm suit on) and it did nothing for my trim that my other bc did not do with the weights properly placed. Underwater I could tell very little difference. I range from a 2pc 5mm to a t-shirt in exposure suits and I don't want to have to go through re-adjusting it every time.
I find many of the "benefits" of a BP to be overrated. The one piece harness for example. Yes it can be replaced cheaply but just exactly how many BC's have you seen worn out? Or there are no plastic buckles to break, again, yes a few do get broken but they are fairly rare, most likely from a dropped tank, not a failure at depth. Give the option of taking a chance on a broken buckle or having to deal with adjusting a BP harness, I will take the buckles.
If I were going to dive doubles or hang stage bottles off it then I would get a BP which is the right tool for that job but for my typical diving- shallow open water they give me no useful benefits.