For the record... I see no real purpose for the BP/W set up... especially the "Hogarthian" set up which is something completely different from a BP/W set up.
BCD's per se do everything a BP/W set up does and a whole lot more. I consider myself a minimalist... and a BP/W is too minimal to meet my minimalist standards.
I have tried BP/W and found it to be inadequate. I had no problems adjusting weighting etc... but why buy simplicity only to have to add all the other things to it? No pockets - you have to add pockets... not enough D-rings... you have to add d-rings, no weight integration - you have to add weight pockets... etc... in the end it looks alot like a BCD.
A well designed BCD with the right number of d-rings, storage pockets, weight pockets, trim pockets etc... can be less money, less headache and a lot safer.
The one true benefit of a BP/W is if it is stainless you can remove alot of weight elsewhere and have it more centered in your core body on your back, so why do some use the ABS plastic or aluminum BP's?
If you want some great BCD's that knock BP/W's out the box... try the new Hollis ATS or HD100 or the Omega Zone II or Scubapro Knighthawk. You could also go with a softpack such as the Dive Rite Transpac w/ Wing and lots of other more common sense options.
I'm sure I'll get beat over the head with this post... but the facts are the facts. If you like BP/W configurations then go for it. I say everyone should dive what makes them happy... We sell BP/W configurations to those that want them... and we sell BCD's to those that want them.
It is not a step up (in my opinion) to go from a BCD to a BP/W... it is a lateral move or a preference... and it is the same if you go in the other direction from BP/W to a BCD.