Guerrero easily. Work rate, pressure, conditioning, heart, and he's much more skilled as a boxer than he gets credit for. Bradley had ZERO punching power at 140, and not surprisingly he's got even less at 147. It'd probably go 12 because of Bradley's solid chin, but he'd be backpedaling the whole time covering up under Guerrero's ridiculous volume punching and pressure. Bradley's a decent fighter with feather fists and a good chin. And that's about it.
Robert Guerrero is a big strong welterweight. Remember how Andre Berto was manhandled by Guerrero? Of course Bradley would not be as stupid as Berto was, trying to join the long line of Mayweather clones. Actually, I think Berto was trying to mimic Adrian Broner. In any case, he just looked downright stupid.
Berto is clearly stronger than Bradley, though Bradley is in better shape. Still, Bradley would rather stick it in the mouth of a rattle snake than to lock horns with Guerrero. He's just not strong enough and he wouldn't have the answers for Guerrero's mauling style.
Bradley's "slick" would not be enough and he'd get beaten up by Guerrero.
Guerrero W 12
Bradley. He's slick, with a great chin, and has been in with much better opposition that Guerrero. I just think at this point Bradley would have too much for Guerrero.