I cannot recommend the Studio Pre enough. I bought mine in January and haven't fantasized about another amp once (ok, maybe I fantasized about a few poweramps but THATS it...)
As for the tonal possibilities, its got gorgeous cleans and juicy, singing, almost vocal-like lead tone. As for that tight metal sound, by my standards its a great metal amp. But I'm not much of a metal player any more. For metal rhythm guitarists where thats all they play, I wouldn't recommend the Studio Pre. Mainly because it does not have a massive amount of gain on tap. Once you max out the Lead channel's gain, you then have to resort to the Volume knob which controls how much signal is fed into the circuit. Once you get into the higher range of the Volume knob you get some nasty farty sounds like as if the signal is maxing out, or like there's "too much" signal. I do use the Volume knob in small doses to add a bit more attitude once I max out the Lead Drive, but as far as I know, the Quad has a bit more of that heavy MarkIII-like chunk which might be what you're looking for. (The Studio Pre has no Mark III influence on its design, where the Quad was designed later and Mesa had implemented a bit of that Mark III character.)
At this point I'm primarily a Jazz/Fusion player so I like my high gain lead tone to be dripping with mids. That's why I LOVE the Studio. But nonetheless, the thing still sounds great when those mids are scooped as well. The 5-band EQ opens up a whole world of possibilities. If you go easy on the Volume knob and use high-output pickups and/or a transparent clean boost pedal, you'll get some great metal rhythm sounds. Though if thats all I played, I'd go for an amp that will give me all that gain natively without the pedal.
So if you're looking for incredible lead tone, incredible clean tone, and incredible hard rock CRUNCH, its all in the Studio. If you want all that plus a terrific Mark III chunk, go for the Quad.