Froch to me is and was overrated. yes he was tough and durable but he was slow, and not exactly a boxing wizard. I think GGG would have won. GGG a better pedigree of fighter .
I'd have to go with GGG late TKO or UD. I know its sparring, but Able Sanchez mentioned how a prime Kovalev gave GGG too much "respect" when they sparred. Kovy is just as big as Froch with arguably more power AND much better overall skills. Not to mention the light heavy and heavy weights that were in awe of G's power. Froch is just too available to get hit in my opinion. GGG will hit him, that much is certain. Theres no way he will continue to take big punches from GGG without showing the affects in some form or fashion. I've seen Froch hurt too many times to think that GGG couldn't do the same in a much more devastating fashion.
If Taylor could knockdown Froch and was minutes away from victory then I'm sure GGG could do significantly better.....
Prime Golovkin was one of the most feared Middleweights we have seen for some time....Even Canelo handed in His belt to avoid fighting Him...Prime he would be to much for Froch even Froch new that.!!!