OK, the main thing to consider here is: Are you actually going to use your 3DS as a legitimate, travel thing. Do you need it to fit in your pocket or a small bag? If so, go with the original 3DS model, because it can be those things.
If no, get the XL. It's not even really a contest - much larger screen without fidelity loss, decent battery life, and all the same functionality you'd want. The only downside is also its upside - larger screens mean a larger unit. So it won't fit into your jeans pocket (maybe cargo pants) or a small bag, but if you've got a messenger bag or backpack, it'll slide right in.
I'm just waiting for the right deal to come along for me to get an XL and transfer all my 3DS data.