Present day GG vs the then undefeated IBF World champion Le Tombeur, with a 80%+ KO ratio, elite level fight finishing bodyshots and aura intact. I think Bute would stop Groves tbh. Which is why I give Groves barely a 1% chance of beating Froch :good EDIT: The reason I say, pre Froch fight Bute, is that his confidence has been shattered since Froch destroyed him.
Bute is a better boxer than Groves and would KO him. Froch just overwhelmed Bute that day and beat him, Groves is a different fighter. Against Bute he would attempt to stand and box, and trade. He is good but not that good. If Groves decides to run then Bute will cut off the ring and get to him sooner or later. Bute is World Class and Groves has yet to prove it. Even if he beats Froch, that would not equal to him beating Bute. Bute posses a totally different prospect than Froch.
Would probably edge towards Bute if I'm honest, GG wouldn't have been able to put Bute under so much pressure in my opinion and I don't think he would of stood and traded. But its meaningless, styles make fights and it doesn't work as such that Froch beat Bute, and Bute beat Groves so that means Froch beats Groves ect