Are you suggesting brakes need to be cooking hot to work properly? I’ve never found that; as soon as any dampness has evaporated off them they’re 100%. Once they get cooking hot performance drops significantly.
I found my pads lasted longer if the brakes were hotter (by using smaller rotors). IME/IMO the increace in power between cold and hot is noticeable if you get the brakes hot enough, I’m 15stone and had 160/140mm brakes for quite a while. You could feel an improvement after the first big pull on the brakes on a decent. They were hope mini’s though, so evey bit of power was needed, better brakes proabbly had enough power from cold!
There was though a very fine line between working temperature and fadeing and eventualy the fuild overheating/boiling. So I swapped back to bigger rotors, the added power of that is far more than added by hot brakes and no need to wory if they’re still going to work by the end of the trail! Great for learning how to carry speed/brake less, essentialy I was limited in how many pulls of the lever I had!
As for the original question, my shimano XT’s aren’t more powerfull than anything else, they just require much less effort at the lever, and it all comes in a very short while, pulling it right back to the bars doesn’t add much more stopping power. I proved that to myself on the 1in3 slope past my house, you could hold the front brake to the bars and the wheel would still roll rather than lock up, whereas my avids would hold it dead (but that’s several times more braking force than you’d ever use, even stopping hard on the road).