In my opinion, there doesn't seem to be a lot of new areas to explore in Xillia 2 from Xillia 1, so going to the same places might wear on you some. Also, there is a big difference in how the parties are handled between the two games. I don't know if I want to say much more on that without spoiling anything. Maybe you already know. For these reasons, I do believe skipping to Xillia 2 would be fine.
On the other side, I feel you learn a lot about the main cast in Xillia 1 that you miss out on in Xillia 2. Please note that I don't read books or play a lot of rpg's outside of the Tales series, so each Tales Story has always at least entertained me, if not completely blew me away, so I don't mind playing through them back to back, but I can understand how it could grind on some people.
Pros of Playing Both:
1) Two full stories that flesh out the characters.
2) Slightly different game mechanics to check out between the two.
1) Revisit the same areas pretty much.
2) Arte Usage doesn't carry over (this kinda bugged me for reasons).
If you are just going to play one, I personally believe Xillia 2 was better, but that is just my opinion. I hope this helps some.
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