The only problems that I've heard of people having with the bps is that its tougher to put back together after being stripped down. For as often as I do that, it doesn't bother me. The first time I did it I had a little trouble getting the trigger group back in but once you figure it out once, the next time is no problem. For some reason the BPS feels like a much bigger gun, and I'm not sure why. The machining, parts fit, and overall smoothness of the BPS is better than a new 870 express or Wingmaster. In that aspect I think you'd have to get an old Wingmaster to match it.
So I guess I'm saying that I prefer the feel of my 870 and I prefer the quality of my bps.