Back when Cowherd was on ESPN (I wish he still was, I haven't heard him since he left, so if he's on Omaha radio somebody please tell me where) I listened to a segment he did on NBA players versus NFL players, and the stats were really lopsided in favor of NBA guys in terms of good dudes versus not so good dudes. Surprised me actually.
I think there are a few factors into the
perception of "good dudes versus not so good dudes" is exposure, season duration, and logistics.
Exposure
NFL: 22 players on the field at a time, only two-platoon systems, players wear headgear. So you aren't as familiar with the players on an individual level near as much other than the stars who get big endorsements.
NBA: 10 players on the court at a time, everyone plays both ways, much smaller area/fans are closer, and you can see the players' faces.
Season Duration
NFL: There are a few players each year who get in trouble right before training camp (late July/early August), then no one pays attention to the preseason (save for fantasy impacts due to injuries and roster decisions), then the regular season and playoffs span early/mid-Sep to early-Feb (5 months).
NBA: They are only
not playing mid-June to late-October. The regular season lasts 8 months.
Logistics
NFL: Successful teams need regimented study and practice together before and during the season. And at most you're only traveling once a week and it's usually on a strict schedule.
NBA: Superstars on a given team can rely on spectacular individual performances, and I'm not sure how much time is spent in the film room (at least for younger players who haven't had to do that much in the past due to being head and shoulders better at earlier competition levels). I know veteran stars spend plenty of time studying to find an edge. But for the younger players, having the confidence to rely on their talent leads to more free time not in the film room. Also, they are playing multiple games each week. Also, there's a lot more travel, meaning more opportunities to F up outside a place you're familiar with. I looked at Boston's schedule (just because they were the first team listed on the page I went to). The Celtics have at minimum 21 different road trips for their 41 away games (might be more if they return to Boston between consecutive road games).
Maybe I'm oversimplifying or looking at non-factors, but figured I'd throw this out there.