I don't think any of the music shops around here have both, so I cannot A/B them. I played around with the RAT 2, but I wasn't able to use it on an amp that was anything like mine, so I didn't really get the full experience.
I'm looking for something new to boost the gain channels on my Peavey XXX (w/EL34's). Right now I have a Digitech Bad Monkey for boosting, which is fine, if a bit transparent. I'd like to have a pedal that can bring a bit of it's own personality to the amp's gain. Having a pedal that can stand-alone is definitely a plus.
The Rat's True Bypass is nice, but not a dealbreaker.
One thing that might be worth mentioning; my tone is rather dark. I have an LP copy with an Anderson HN3+ in the bridge, neither of which are generous with the highs or high-mids. I can kinda dial it out, but even that is not as smooth as, say, having a guitar made of naturally bright(er) wood or a bright pickup.
If one of these pedals is not able to compensate for the lack of highs, speak now.