They're both goodish, but none is anyhwere near the best Sci-fi RPGs, which are:
Fallout 1 & 2 (better story, characters, customization, meaningful choices... basically better than ME/FO3 in everything except graphics)
EVE Online (One of the best MMORPGs ever, and the one closest to true Roleplaying)
Anachronox (almost no choices, but a great, charming and funny story with great characters)
Kotor 2 (great story, writing, characters, some meaningful choices and has Kreia.. better than Kotor 1)
I might be missing some







