I haven't really gotten far into Phantasia so I can't comment on that.
I prefer Symphonia to Abyss, but I'd say they're pretty close in quality. I prefer Symphonia's cast and story and such, though Abyss has an edge in gameplay with Free Run and mystic artes.
--
http://img.imgcake.com/GuessMyUserName/mask_salesman_rage.gif