I can't believe there's actually a question on which is better. o.O; A good look at the episode discussion topics hints that there was more of a positive opinion for last season.
A bit too much 'wtf did they do to Syaoran's eyebrows/face/body/head?' animation and fillers for my taste in the second season. First season has my undying love. Though, if they manage to do Tokyo in the second season, and do it somewhat well, my opinion may change.