I don't consider either of them particularly outstanding. The only title that I thought Sakaguchi directed notably well (FFI-V and Spirits Within, from what I know of. Haven't played Blue Dragon yet) was FFIV and the only game that Nomura directed that I thought wasn't half bad (Advent Children, KH I and II) was...actually none of those are notable in any way at all.

Apart from that, the two aren't particularly comparable. Nomura is and always will be a character designer at heart, something which I've never heard of Sakaguchi partaking in. They both also have random writing credits in various games, but they've never really revealed how much they influenced the games themselves to make any real judgment. We'll see how Blue Dragon and FF Versus XIII turn out I guess.