But get a New one since it's kinda just better in every way.
GameStop doesn't have a blue N3DSXL on their website because NA never got the blue one, just black and red. (Plus a few special editions, but none of those are blue.)
Seems like you've already made the decision to get a New, and if that's the case then this post will do little but reinforce that decision.
Recently, my Midnight Purple 3DS decided that it didn't want to have a properly functioning bottom screen anymore. I was forced to upgrade and was put in pretty much the same situation of deciding whether to get an XL or a New XL. I personally chose an XL because it was cheaper and I don't figure I'll use my amiibo for anything other than Smash and decoration, so the New XL's functionality would be lost on me.
That said, the New is only a little bit more expensive than an ordinary XL, so it shouldn't make too much of a difference for most people to pay that extra amount. For the increased power and the ability to play games that would be exclusive to the New XL, it's an easy decision. I figured I can live without those exclusives, or at least I can until I have more income.
The only thing you need to know going into this is that if you want to use a different microSD card with more GB, you will need a very specific screwdriver to take the back off of the New XL to be able to get to the card. It is a #0 screwdriver.
Additional stick, used in Smash bros, as well as other games (you can control the camera in Majora's Mask 3D and Monster Hunter 4 Ultimate, for example).
Face-tracking 3D, much better than the original's 3D
Better processing power, most noticeable in loading times and downloads (also allows you to play Xenoblade Chronicles which is only playable in the New versions of the system). Home screen themes also load faster.
Built-in NFC reader for amiibo.
I really like mine, and I can feel the improvements. If you need a new one anyway, I'd definitely go for the New 3DSXL.
I would go for a New 3DS XL as I will be getting one myself after I get my PS3 Slim. Since it comes out of the box with amiibo support, a second analog stick (C Stick), and extra shoulder buttons, and a better CPU, I would get this over the 3DS XL as it will perform better and control better in most games.
Absolutely go for the New 3DS XL. As others have said, there's more 3D stability, and if you play Smash Bros, HHD, or any other game that requires a separate scanner for amiibos, you're better off with the new one. If you don't already have a reader, it'll save you a little bit of money at least, I think. Also, I'd say the fast speed alone is a good reason to go for it as well.