I have a couple of reasons why I prefer the 870 over the bps.
The 870 is quicker and easier to load or unload with its side loading/eject port. The bps is magazine fed for every shot. This means poking and shucking to chamber a round.
If you don't have your hand forward on the Fore stock, your hand can block the bottom eject port and jam your empty on the bps.
I'm not a fan of the top mounted safety. I've seen them get unknowingly knocked off safe in hunting situations.
Having said my piece, I must also state that IMHO......it's never a mistake to buy a Browning.
My quail hunting buddy carried a BPS. That's how I know about it.
The reason he had a BPS was because his 870 blew up a 'nannered the barrel into his thumb.
There you go....thats all i have to say about that.
Best wishes...choose wisely .