I've owned both mk1 Focus RS and mk2 Focus ST and for me personally I liked the RS the most. The only regret I had with my RS was that I sold it!

The main problems imo with the mk1's are that they are old cars now so getting worn out, rust problems, some hard to get parts etc and also some of the prices are crazy now! I'd still love another though but I doubt I'll get one. I don't even drive a Ford anymore, I've gone VAG instead!!