Uematsu is really good with event music. His opening/endings are almost always nice to listen to. But overall I find most of his in-game music to be pretty boring. There's a few exceptions here and there, almost the entire FFVI soundtrack included.

Mitsuda, in my opinion, comes up with great music for both events and in-game play. Not to mention how diverse his style is. Typical fantasy RPG music (CT), pretty celtic tunes (XG, CC), and then dark, almost gothic choirs and orchestral pieces (XS). Yeah. I love the Mitsuda.