Bigger gloves are useful for defense. You can catch a lot with big gloves that you can't with little ones.

What's gonna matter most is how the athletes train, how hard they get hit in sparring. A very long professional career might be 30-50 fights, but that's thousands of hours of training. If you're spending much of that sparring hard, even if you don't get many concussions, the cte is going to build up