Re: Sorting Out The MXR Dirt Boxes....
It's not too bad...
Custom Badass 78 Distortion-Based on the original Boss DS-1 with a few tweaks-If youlike the DS-1 you'll likely enjoy it, if you don't keep walking.
Custom Badass Modified OD-This is based on the Way Huge Green Rhino which is of the TS/SD camp of OD-soft clipping, etc btu with some nice added features for tayloring the lows and mids.
Fullbore Metal-I think it sucksk but I don't like those metallic/scooped metal tones, the built in gate is a great idea for these types of players.
Blue Box-Gated fuzz with sub octave-pretty crazy sounding pedal truth be told but it has it's uses...Listen to the solo on Fool In The Rain.
Classic 108-This is based on the jimi Hendrix Fuzz Face, it has an added buffer (so it can be used wiht a wah pedal) and is in a smaller box, it is not handwired and forgoes a lot of the mojo parts but is still a good sounding box if you like vintage Silicon Fuzz Faces
Distortion III-This has nothing to do with old MXR Dist pedals, it's smoother and has a MUCH wider range of tones. I'm surprised I don't see this box being used more truth be told. If the Dist III cost $250 and had a 6 month wait list it's be massively popular! A long time staple of Keith Urban FWIW.
Distortion +-This is the newest version of the Dist+...thin, buzzy and sort of crappy IMHO but some guys like it.
Script Distortion +-Mid 70's style reissue of the original, can only be had at PGS.com, all the issues of the original buyt all the cool tones too...Think Randy Rhodes!
GT OD-TS style OD pedal, low gain, soft clipping, a little more gritty than a TS-808, a little more low end than a TS-808, another GREAT pedal and I do see this one a good bit being used.
Dime Distortion-No idea, I assume heavy as hell!
ZW Berzerker Overdrive-Based on Zakk's Boss SD-1 pedals but with more volume, more grit and more low end.
I hope that helps a little.
FWIW, Jim Dunlop has a GREAT website and there are clips and vid's of all of these pedals on there...not the best way to start looking but a good way to narrow it down a bit.
http://www.jimdunlop.com/products/electronics/mxr