I've not dove a BP/W. I use a Sherwood Avid BCD. While it may not directly address the original questions, perhaps my perspective may be of small service. I have not yet attempted to move to a BP/W for a number of reasons.
1.) I trained in, knew how to use and own a jacket BCD.
2.) To choose it, I stood in a dive shop discussing BCD choice with the owner, tried it on, and ordered the 2x size from him. One decision; Sherwood Avid vs. other brands of very similar product.
3.) It works for what I do (rec., no tech., diving, mostly tropical Caribbean diving).
4.) I usually don't wear a wetsuit and don't dive doubles.
5.) I love weight-integration; I'm shaped like a bowling pin and spun like a top with a weight belt in an OW class dive. No more!!!
6.) I cram an SMB in one pocket, and a spare mask (when solo diving) in the other.
I'm not a technically minded person. I strongly dislike being confronted with a range of confusing decisions, and the anxiety of having to commit and the risk of making a wrong choice. If I'd walked into that LDS and discussed BP/W, it might've sounded more like this...
1.) Do you want a steel backplate or aluminum? There are different brands.
2.) Do you want that plate padded or bare?
3.) What wing you want with that? There are different brands. Do you want single or dual bladder?
4.) What about webbing? Oh, you don't know what that is? It's these straps that come across you to hold it on you. Do you want some sort of comfort straps?
5.) What's that? Oh, a crotch strap, of course. What, you don't like a strap wrapped through your crotch? Well, sorry about that...you'll get used to it.
6.) What do you want integrated weights for? You won't need as much weight as with a jacket, and can wear a weight belt. Oh, you hate weight belts. Yeah, you can buy some weight pockets. What brand?
7.) What do you want pockets for? You don't need all that fluff. Oh, your spare mask and you don't want your SMB flopping around. Yeah, okay. Do you want pockets on your webbing, or glued onto your wetsuit? Don't wear a wetsuit much? Okay, what brand of pockets? What size?
8.) Okay, we need to get this stuff on you so we can customize the webbing to fit you well.
To put this in perspective, when I take my car to Walmart for routine servicing, I want them to 'just fix it,' charge me the 30 something bucks & let me go. I get mad when the service guy insists on discussing the different oil product options and resists just recommending one. Any attempt to discuss auto mechanics with me is apt to earn a hostile glare.
Now, I get that there are substantial advantages to a BP/W, especially for some types of diving. But to get me in a BP/W, 1st you have to earn my trust in your knowledge and understanding of and loyalty to me, sell me that it'd be worth several hundred dollars for diving like I do in Bonaire, make most of the decisions for me, understand that I probably won't lift a finger to customize it myself later, choose all the brands for me, make it fit on me, make it simple to use and the one decision I might participate in would be aluminum or steel backplate.
Or, I could just keep diving the Sherwood Avid BCD, which seems to work fine for the diving I do.
Richard.