I like both fighters. I believe Calzaghe's resume is underrated, as the opening poster mentions he fought a lot of current and former world champions, and unified 2 divisions, he doesn't really get the credit the deserves. The Eubank win inparticular is underrated, Eubank was slightly past his prime but no way was he shot, after the Calzaghe fight he came very very close to winning the cruiserweight belt against Thompson in 2 classic fights. Thompson was a 3 time world champ and a very underrated fighter.
The problem with Calzaghe is for every Kessler there's a 2 or 3 Manfredo Jrs. Calzaghe's resume is good, but its padded, and could've been better. He could of gone to Germany to fight Ottke, I know Ottke received a few gifts in Germany but Calzaghe would've beaten him comprehensivly IMO. He could've also fought Johnson in the early 2000s and unified the division sooner. To be fair to Calzaghe there weren't many 168lbers at the time that he ducked or didn't fight.
Froch's resume isn't as good yet but if he beats Kessler in a rematch and has 1 or 2 more good wins he'll be up there with Calzaghe in the ATG 168lbers.