Broners a decent counterpuncher but he's also done now. If he got plenty of notice and they gave him a comeback fight first and he gave it his all then I would probably consider him to maybe stop the Benn express. But taking everything into consideration I'll pick the young, fresh, in form Benn.
To wit, a legitimate stoppage, and not a stoppage of the British variety where a fighter gets buzzed by two shots and the referee jumps in and waves it off way too early.