I think some other big factors are:
(I think all of these still fall under ignorance and an unwillingness to learn, as well...)
1. A lot of people really don't have experience with either cartridge.
Most people have not shot a 10mm (in any form), and even fewer have shot a .41 Mag. Still fewer have shot both. So, most of what they know, they read on the internet (or from the former "Air Force Special Operations Police Instructor" -- also a Medal of Honor and Distinguished Flying Cross winner - trying to enlighten everyone at the gun store by incessantly spewing filth from his face hole). (Don't worry. If you missed him, he'll be back with his own bar stool from 1-6 pm Mon-Thu next week.)
2. Some people have a very difficult time looking past their own uses or desires for cartridges and/or firearms.
If I only punch paper with a 9mm and a .22 LR, then 10mm and .41 Mag are going to be the same to me: Unnecessarily punishing and wasteful.
Along similar lines, a lot of people like "light for caliber" bullets in nearly everything they shoot, while other people use everything or like "heavy for caliber" bullets. Those habits/preferences can be difficult for some people to get away from when comparing things.
3. People get stuck on stereotypes and gun rag misconceptions.
Myself and a few other people on the MarlinOwners forums built ourselves some .307 Winchesters on Marlin 336s in the last couple years. Dozens and dozens of otherwise seemingly knowledgeable shooters could not get away from the age-old stereotype that the cartridge is barely a step up from .30-30. We pounded into their heads that it comes close to, and sometimes even exceeds .308 Win velocities from 20-inch barrels with 180 gr bullets (and greatly exceeds .30-30), and that 150 gr bullets were only a little bit shy of .308 Win ... while running notably lower chamber pressure. But, the lemmings continue to follow the writings of their infallible gun rag favorites. Now, Hornady has a 160 gr load with a muzzle velocity that matches or exceeds a great number of .308 Win factory loads, and it's being viewed as, quite literally, a "myth" by the guys that still buy into the stereotype.
(I'll be honest and say that my particular rifle is
way down on velocity. It is, in fact, not much of a step up from .30-30. But they aren't all like that. I just happened to roll craps while the rest of the guys got lucky. Every barrel is an island unto itself...
)