The credit "Brandy ft. Chris Brown" is just how the record industry works these days, and it's something we really just have to get used to for the moment. (If mass outcry had any deterrent effect on what labels did, certain remixes would not exist, and certain folks responsible wouldn't have responsibilities anymore.) The Bangladesh and Sean Garrett writing/production credit is also how the record industry works these days; judging by their past work, it's one of the better ways. A Brandy comeback, however, wasn't exactly inevitable, and yet here it is, meaning we're predisposed to like "Put It Down" much more than if someone else's name were on it.
Pay attention to that last bit as you listen to this, by the way.
"Put It Down"'s certainly an assertive lead single, largely thanks to Bangladesh and his bass/string stabs. Everything else here's the thin soup of too much chart R&B--the tinny percussion, the canned claps, the "I'm gonna put it down / you're gonna fall in love" chant that's the tough hook to the chorus's sweet one--but those stabs! They almost singlehandedly make this quite the beat, enough that it almost doesn't matter what the vocalists do over it.
That's probably for the best, because no one here sounds like themselves. Brandy's voice, when not massed into (very nice, mind you) call-and-response, is either kept sliver-thin or made slightly affected, as if someone in the studio kept yelling "SWAG! MORE SWAG!" across the room while she tried to record. Meanwhile, Chris Brown's verse is so chirped and pitch-shifted and accent-addled that you suspect this was meant to say "ft. Nicki Minaj" before someone at RCA remembered it was supposed to be a hetero love song. (Or, while we're playing conspiracy speculator, maybe Brandy's verse was supposed to be Chris's, making this Chris ft. Nicki? Brandy sounds a little like Chris Brown backing vocals.)
The beat, though. Some things can excuse a lot.