I've only used the Revv G2. It's a very cool pedal, but I'm thinking of selling it if you're interested. Not because I don't like it, I just have too many overdrives and this is a fairly "modern" sounding one. I have two amps right now (Mesa Triple Crown and 1965 Fender Pro Reverb), so I use the Mesa for modern sounds and the Fender for vintage sounds, and the G2 doesn't really fit a niche for me since I don't need it with the Triple Crown.
It's not exactly an overdrive in the sense that I wouldn't use it like a Tube Screamer to push an amp into saturation. It's more a preamp/crunch pedal that sounds best going into a clean amp in my opinion. The EQ section is very flexible and it sounds good with both very light gain and medium levels of gain. The Aggression toggle switch is nice to give you more voicings. It's not a compressed pedal, so you can boost the pedal itself with another pedal for good results. It tracks fast and is tight, which I guess is why I think of it as sounding so modern.
There's a video from That Pedal Show that ran through a lot of settings and is much more honest than other videos I've seen. You can get it to sound like a mid-humped Tube Screamer (though again I wouldn't use it the same way that I use a Tube Screamer) or you can also get it to sound like an improved Boss BD-2, as well as other sounds. The "improved BD-2 sound" is probably my favorite. Here is that video:
My final verdict is that it's a great pedal if you want to create a separate, low gain channel for your clean pedal platform amp. Otherwise I wouldn't recommend it if you want to push an already cooking tube amp.
Mine is completely mint with the box, etc., and I don't really have a use for it, so PM me if you want to save some money on one.