Charles was arguably the greatest light heavyweight ever. Didn't have too much trouble with the great Archie Moore. So I would pick Charles over pretty much any light heavy.
Like I said, Lewis was great and he doesn't get mentioned enough... still I say Charles was better and his resume was better. Slapsie Maxie Rosenbloom was tough to beat, as a matter of fact he went 3-2 vs. Lewis. Elmer Ray lost to Lewis (LKOby12) but he was only 5-7-3 (2) going into the fight. He had recently been stopped in 3 rounds by Jersey Joe Walcott. Needless to say he had not yet peaked when he fought the much more experienced Lewis. Jimmy Braddock- he went 1-1 vs. Tiger Jack Fox- good fighter, good win (KO3) Al Ettore, Al Gainer, Bob Olin, and company- good fighters but not as good as Bivins, Marshall, Burley, Maxim, Moore, and some others. Lewis over Moore? I doubt it. Lewis is more on the Harold Johnson level IMO, no shame in that. Yes, Johnson beat Charles but the fight was very close and Charles was 137 years old.
Short footage of Lewis knocking down a sparring partner: http://www.efootage.com/stock-footage/61547/Philly_Boxers_Train_For_Upcoming_Fight/
A lot of people have said a lot of things. George Foreman said Reggie Johnson was an all-time great LHW. I like Reggie Johnson and he probably could have done a little more in his career with a few breaks here and there but overall he came up a little short in his biggest fights. At LHW he really didn't do too much. Mickey Goldstein told Rocky Balboa that if he could catch a chicken he could catch greased lightning. He also told him he was gonna eat thunder and crap lightning. Anyway, opinions are like assholes... everybody has one and most of them stink like ****! I'd rather look at what really happened and base my opinion in fact.