I liked Abyss a lot (and Symphonia too).
Luke's annoying. When he's still saying Master Van 55 hours into the game, it can get really annoying. Anyway, gameplay-wise, it's pretty much the same as Symphonia. The story isn't really strong enough to justify the 60-80 hours of playing IMO, so whenever you see sidequests, take them just to break up the main quest. It's also a lot more fun to play with another person, so if that's a possibility, do it.
Anyway, good luck and have fun.