It has to be Taylor no doubt. He had to KO taylor to win, thats what makes it special, because he was getting his ass handed to him through the fight.
I guess it depends on how you define "best win". If it's just based on the opponent and the outcome I'd say Dirrell (who I thought beat Froch convincingly). If you throw performance into the mix I'd go with Abraham because in that fight he was a slight underdog coming in and won 11-12 rounds convincingly.