right now, i'd have to say the older MS explorer. I don't like logitechs new design, and i'm fed up w/ their drivers. MS's new explorers side buttons are not very good IMO. The wireless one kicks ass comfortwise.. but it's wireless and didn't work well enough for me. Of course, i'm biased towards curved mice only (and preferably below/close to $30 if i can find it) more comforting.