Neither. The 3DS is a waste of your time and more importantly it's fruit: money.
If you think the 3DS is a waste of time then that's fine, the problem here is what you just posted here did not contribute any valuable information to the OP's question.
Fennis didn't ask if he should spend money on a 3DS or not, he asked what model he should get.
I just wanted to point that out.
OT: OP should go for XL.