It's definitely worth revisiting and finishing them both. They really are meant to be played together, and the true ending unlocked by beating them both is immensely satisfying!
I like Seasons better, probably because (as others have admitted) I played that one first. However, other pluses to that game for me include a more interesting hook (changing seasons) some better items (Roc's cape) and what was to me a better side world (Subrosia vs. Crescent Isle).
That said...