Here's a visual comparison of the Brainwavz pleather vs. stock vs. Sound Professionals velour earpads. The Sound Professionals velour earpads appear to be slightly thinner than stock but are still really comfy. They fit quite well on the ATH-M50x. The Brainwavz are very comfortable but they do make your ears feel sweaty after a while.
NarzI personally prefer the pleather ear pads from Brainwavz over these velour from Sound Professionals, mainly due to comfort levels for long sessions. The Brainwavz are spacious and feel great, aside from the fact that they do get warm and can make your ears feel a bit sweaty. The velour don't get hot, but after a few hours of gaming, the slight pressure against your ears starts to hurt. (Looking up "outer ear anatomy" on Google, it's the helix and tragus that hurt.) So for my personal use case, I prefer hot/sweaty over annoying pain. There are some red and black velour ear pads from Brainwavz, but I read that there is a noticeable change in sound signature with those.
I actually got my Brainwavz ear pads before I got my ATH-M50x headphones. I didn't really mess with the stock pads.
skrooksSame here. I've used several different ear pads with my m50x, including these Sound Professionals velour and Shure SRH840 pads before finally landing on the Brainwavz HM5 pleather ones. They are much more comfortable than stock pads, and I can wear them for longer without discomfort. In terms of sound, other than sounding more separated, there is no noticeable difference.