Pavlik would stop Benn, most likely. Better skills, better chin, better stamina, higher ring IQ. However, given how straight up and hittable Kelly was, you have to make Benn a live dog. It wouldn't be a huge shock to see him come from behind and blast Pav out. I'd fancy Pavlik by TKO though.
I'd make Pavlik a strong favorite. His style should shine againt an aggressive looping puncher such as Benn (as it did against Miranda)
Yeah I think Pavlik has to be favoured to exploit Benn's wide punches. If one gets through flush though, it'll be an issue.