Well, I can only reference my old 5150, but the difference between the rhythm (clean) and lead channels on it were like night and day. You could of course set the volume to be whatever for each channel, so there wouldn't be or would be if you wanted a difference when switching between the two. The clean channel basically only utilized 1/2 of a 12AX7 for the gain stage. The crunch button on the clean channel would let you push the amp into that ACDC crunch by engaging another gain stage when you turned the gain knob up. The lead channel utilized all three 12AX7's for full sizzle of 6 gain stages. That amp would play clean at full volume with the crunch button disengaged and the pre-gain knob turned down. Loud. I mean REALLY loud and clean. Fender Twin loud and clean. The lead channel was exactly that. An example: with the lead pre-gain set to 6 and the post-gain set to 6, and 2 12" sheffields in the sealed cab I could keep up with and surpass many times the 4x12 cab and JCM900 Marshall the other guitarist was using. I usually had to turn down in the mix. The amp had a really good distortion sound as lower volumes as well. Not fizzy like most amps, but even at a post volume setting of 1 it was way too loud in my practice room.
I hated to get rid of it, but it just wasn't practical.
As far as your amp, what market are you wanting to cater to?