I've noticed in my band that sometimes they tell me I need to turn down, and I can barely hear myself......Same goes with Brad, our other guitarist, we'll tell him to turn down a little and he goes "I can't hear myself".

My theory is that it's hard for you to hear yourself in a band b/c your playing the notes and all those notes or chords are running through your head as your playing it. You hear what's in your head rather than what's actually coming out of your amp when the level's are actually equal. So in turn, to hear yourself coming through the amp, you must be louder than everyone else......Just my theory on how this all works with my ears...

But Jon is right also, when you have 2 guitar playing, they have to be eq'd differently or they blend in and the sound gets muddy...