The other guitarist that I play with most is my brother. We're like one organism when playing together. Whoever is playing rhythm just naturally backs off a bit without letting the song energy fall flat. When I play with a "one-volume basher" I'm always astounded that they have no sense of the dynamics and interplay - just bash bash bash.
I played with one of those in a recent band, and they were so bad that they would step on their boost each time they heard me kick mine in for a solo. I hated every minute of it and the experience has totally put me off two guitar bands.