To be honest, I'm going to be leaning more towards the XL, despite me having a regular 3Ds.
For one thing, of course, Nintendo had decided to increase the thickness and size of the A, B, X, and Y buttons as well as the Circle Pad. What does that mean? Well, honestly, for me, that would mean that it'll be way easier to use than the 3D's version. Typically, larger buttons means you can be less accurate and still press them easily. With the Circle Pad it should be nicer to use for larger thumbs and the thickness is sure to make all the buttons feel of a higher quality. The same design change has been applied to the L and R buttons, making them bigger and thicker.
Well, of course, maybe you need to try a demo one at a store before making a final decision. Again, I've got the first 3Ds, and to me it's pretty portable, where you can easily fit it in your pocket. Since you don't have one, it depends on what you prefer, in my opinion 3Ds XL looks better, but, no matter how many ways I look at it, the 3DS had always pull of it's standard qualities. The 3DS is still awesome, so, you can perfectly lean to that if you want a cheaper game system, but, for more "quality", I'd say the XL.