ccs or hi-tech
Hitech: efficient, ansi compliant, nearly zero pic specific functions, expensive. I used it. It's very good and i think it has good features for pic type µcs over ccs where efficiency is critical.
CCS: I only tried it. I think not ansi compliant. Has lots of pic specific functions which may make easier to use if you don't very familiar with the pic but according to me decreases efficient use. Cheaper. I think if you do smaller projects often, it has advantages over hitech but according to me hitech is better.