Studio .22 for sure. The Quad is insanely big (4U) and too much crap to try to have in a rack. 4 spaces for the pre only means 2 for the poweramp, 1 for the power conditioner, and 1 for the FX. Thats 8 SPACES! Sound wise I really dont think it it better, just more channels. You would be better off getting a studio pre, and a formula pre which is 1 space, 3 channels and has a better clean sound then the Quad in my opinion. (5 channels total in 3 rack spaces) Thats my 2 cents.
I owned a studio pre for 2 years with a 50/50 and I tracked some of my best, most beautiful clean and dirty tones with it ever. It was a fabulous sound and I regret letting it go. The quad is nice, but I have a Roadster for my 4 channel thing.