The Criterium series was named to differentiate the big and small downtube versions of the same 3.0 frames. Crit had big downtube, RR had smaller/normal sized ones.

http://www.vintagecannondale.com/
They'll have all the info you want. 1990 has both the Crit and RR 3.0 frames.

Earlier than the 3.0 series all the frames were basically the same, those had the enormous seatstays. "Crit" frames, also named "SRxxx" in bike model numbers, were just racing versions of their Touring frame, which is the first frame they made. Look at 1985 as an example.

The earlier frames had steel forks, the later ones had aluminum ones. They were all pretty harsh riding relative to today's frames. I remember swapping bikes at a race after a crash - ditched my Cannondale 2.8 framed bike (from 1992 - which wasn't too easy riding either) and grabbed my 3.0 crit bike (I had a whole bike in the pits due to incompatible something - I think 7s vs 8s and friction vs Ergo/index). My hands went numb pretty quickly on the 3.0 and I used the same bars, stem, seat, pedals, tires, and more flexy rims. I dropped out pretty quickly after that.

cdr