Ok... Splawn vs. my '71 SL
Splawn:
Tighter, gainier, mids are more modern. It's hard to describe. The amp sounds more polished to me.
Super Lead:
Looser low-end. Not in a bad way, but it's more of a classic-rock low-end. Mushier, think VH. You can't palm mute like you can on a Splawn. The mids are raw and maybe more nasally. Also, not in a bad way but it has different mids. Obviously less gain. The Super Lead is alot more raw and classic-sounding.
If I were to compare a Splawn to any Marshall, tone-wise, it's much closer to a great 2203 than to a Super Lead. Picture a great 2203 with alot more gain, less ice-pick and a smoother presence. Yeah also a tighter, bigger low-end.
I find my QR to not be bright at all. But that's probably because I use GB's.