I found the Crystarium to be about equal to the sphere grid. Sure you need insane amounts of CP learn the non innate jobs, but in FFX you weren't really going to round out yourself completely with all types of abilities without a great amount of post game grinding either. Seemed about the same to me.

The story of XIII seemed kind of half assed to me, whereas in X it seemed much more fleshed out and complete. Only problem was I didn't like X's story in the least. So I get to chose between disinterest and aggravation. Whee!

I liked the 'dungeons' of FFX a lot more, but I am going to attribute that to my general distaste of designing areas based around a movable camera. Discounting the negative implications forced on the game due to the camera I would say they would both be equal.

Gameplay is about the only significantly different factor for me. I though battles in FFX were very fun, and the only saving grace of the game. The battles in FFXIII were merely adequate to keep me from quiting the game in boredom.