I would say Floyd's resume is better, but not by THAT much... "ten times better" is taking the piss. They are both in the same tier (top 15-50 ATG) and there isn't much separation.
Here are my arguments why, feel free to counter them one by one but please none of the three Fs: fanboyism, femininity, or fake "facts"... ain't no facts when evaluating resumes. I am actually trying to find a SOMEWHAT objective way to rank ATGs though, so any feedback as to my rationale and which categories you think should be most heavily weighted is welcome:
R1-R4: High Quality Wins (Floyd, close): Both guys have a similar number of high quality wins. Chavez has Azabache Martinez, Mayweather, Ramirez, Lockridge, Rosario, Limon, Cortez, Taylor 2x, Hernandez, Camacho, Randall (12)... Whereas Floyd has Hernandez, Corrales, Chavez, Castillo 2x, Gatti, Mitchell, Hatton (great win IMO), Judah, Oscar, Shane, Cotto, Pac, Canelo (13).... You could give a take a few on either side for sure... my point is it's close with a slight advantage to Mayweather. (This is the most important category but also the most subjective, so I'm not sure whether to assign 4 rounds to it or not.) (R1, R2: Mayweather, close, R3: Chavez, close, R4: Draw)
R5-R6: Solid Title Defenses (Draw):: Both of them have a lot of defenses against decent contenders (Maidana or Haugen types)... Chavez probably has more but Floyd's opposition may have a better W/L percentage. Feel free to do the research, I am too lazy. (R5: Mayweather, close, R6: Chavez, close)
R7: Legendary Wins v. ATGS (NC): One big knock on JCC's resume is that he definitely LOST when he fought a prime top 50 ATG in Whitaker (and it wasn't close IMO... I usually respect the judges' decision but this one was a ****ing joke)... but Floyd didn't fight Oscar or Pac in their primes so we'll never know on his end. Neither guy has anything like Ali over Liston and Foreman, Ross over Canzoneri, or SRR over prime Gavilan or Basilio. This keeps both of them out of the top tier. (R7: Draw, 9-9)
R8: Manner of Victory (Chavez, clear): When comparing resumes, some attention has to be given to HOW fights were won... prime Chavez destroyed most of his greatest opponents... Mayweather has some good shutouts and stoppages (Hatton, Canelo) but a lot of close and questionable UDs as well (Castillo, DLH). (R8: Chavez, clear)
R9: Titles, Weight Classes, Accolades: (Floyd) : Floyd's 15 titles across 5 weight classes clearly takes this one, though JC was no slouch... I believe he's second after Joe Louis for most consecutive title defenses. I didn't assign this one any more than a round to adjust for era... One belt or two classes in the one belt and eight class era is as or more impressive than four belts or four classes in the era of alphabet belts and weight class ****ery (i.e. pit stops in weight classes just so you can say you're an "x-divison champ"). (R9: Floyd)
R10: Activity, Overall Record (Chavez, clear): OP's argument that we can completely disregard Chavez's early record against club fighters is facetious, IMO, as activity and quantity counts for something. We don't know **** about Chavez's early bum of the month club in Culiacan, but beating the **** out of a different guy every two weeks is impressive no matter how you cut it... This is another way to adjust for era--JCC came up at the tail end of a harder era and that's important. (R10: Chavez, clear)
R11-12 (Championship Rounds): Fantasy H2H Matchup, Prime for Prime (Floyd, close): JCC struggled with great boxers like Taylor and Pernell, while Floyd excelled against pressure fighters so I think Mayweather takes this. However, the JCC of the Rosario and Taylor fights would've given PBF everything he could handle, I believe... That fight probably would've played out like the first Taylor fight (sans stoppage) or the Floyd-ODLH fight, imo. (R11-12: Floyd, close)
R1: Floyd, 10-9 close
R2: Floyd, 10-9 close
R3: Chavez, 10-9
R4: Draw, 10-10
R5: Floyd, 10-9 close
R6: Chavez, 10-9 close
R7: Double KD, 9-9
R8: Chavez, 10-9
R9: Floyd, 10-9
R10: Chavez, 10-9
R11: Floyd, 10-9, close
R12: Floyd, 10-9, close
Verdict: 115-113 Mayweather in a UD with a lot of close rounds... surprise, surprise. I could also see 116-112 Floyd, 114-114, or 115-114 Chavez, but NOT a domination from either guy...