Very tough call. I think the best win between the two of them is Chuvalo's KO of Jerry Quarry. Therefore, I will say beating Chuvalo is a bit better looking on a resume.
I'd go with Chuvalo he gave a prime Floyd Patterson 12 tough rounds, went 15 rounds with a prime Muhammad Ali giving him a good argument. And also should of been of the Heavyweight champion, he was robbed against Ernie Terrell. And he also has the best win out of the two with a win over Jerry Quarry.
If we're being brutally honest, Chisora is a British/domestic level fighter. The only reason he lasted this long at the world level is because he has a granite chin and plenty of stocky mass to keep him from getting stopped all the time (well that and having superb Matchmakers/promoters to trick people into thinking he's elite). Not that Chuvalo is some sort of A class elite fighter either, but he was usually much more competitive even when he lost compared to Chisora. Chuvalo looked like he belonged there, and oftentimes Chisora didn't. Not much separating their resumes aside from the Quarry fight, but in terms of skill/the eye test, I'd also lean towards Chuvalo a bit.
Chuvalo because you're in better company having him in your win column - Ali, Frazier, Foreman. If nothing else it looks good. Even so, I'd still go George for the reasons Glass City Cobra gave. No need to repeat them.
In between the great fighters that motivate me to be passionate about boxing, characters like Del maintain the love for it, ya'll. There aren't many guys that constantly provoke the incredulous brow/goofy grin combination facial expression like this man. I can feel my face doing this throughout his airtime.
