Groves is still only 25 and is clearly really coming on physically. No doubt he hits harder.
Froch's no stranger to taking flush shots on his tough chin, but Groves's had him hurt several times.
On single-punch power, I think Groves. His knockout punch of Francisco Sierra was insane. But Froch has a lot of overall upper-body strength and stamina which gave him his success in the pocket in the last couple of rounds last time around - he was just a touch stronger in the exchanges. One might say Froch is more "heavy-handed".
they got different kind of power. Groves is explosive and fast. Froch has heavy hands, he puts all his body behind his shots, dosen't tire and breakes his opponents down with accumulation of damage. You don't see groves punches coming from a mile away so it's harder to prepare for his shots. You see froch punches coming but they still hurt you because he hits you everywhere and as you brace for the first one he loads up on another one or two.
Single punch power?
I think Groves does by a bit.
More than a bit, Froch relies on his unbelievable stamina to wear down his opponent then bangs them out with combinations late..
Bute was a different matter, because he's got terrible resistance
Edit.. I still think Froch takes him in the rematch tho
Groves, more explosive. Froch wears you down, most of his KD/KOs come in the later rounds against the better opponents he certainly has heavy hands though.