I think the LaLonde version of Leonard was still sharp enough to pull out a close one against Frochy. Ray's handspeed would give Froch a lot of problems.
LaLonde had a helluva right hand, and Froch was twice dropped hard by guys with right hands not as powerful as Lalonde's. Yeah, I would give Donny a shot, but obviously Froch is the favorite in that one.
Froch would step forward with his right foot and square up when he threw a right hand. George Groves timed that and made him pay for it. I expect that Leonard will time him and nail him flush with a right hand. How that affects Froch will go a long way to deciding who wins this fight. The next factor would be how often Leonard lands his right hand counter to Froch's right hand. Because he does it all the time. Years ago I read an interview with Gil Clancy and he talked about how his son wanted to learn to box. He took his son to a gym and the 'trainer' was teaching guys to throw a right hand and square up like a baseball pitcher in the follow through. He took his son out of there because he didnt want him to get killed.
I do think Froch was more skilled than he might have seemed to a casual onlooker. Whether it's enough to overcome a master like Leonard I don't know, but obviously the size differential has to be factored into the equation. I'd lean towards Leonard but not with any confidence.
