I got a used New 3DSLL (the Japanese version of the XL) mainly to play the Japanese release of the Sega 3D Classics collection - there were a handful of games that weren't ever brought over with the Western releases. It's a great series and M2 added some cool optional customizable settings and updates to most of the games (e.g., switch off the collisions in Super Hang-On, or select from different cars with varying capabilities in Out Run, steer using the gyroscope, etc.). The Fantasy Zone updates are even more elaborate and worth exploring, including a System 16 upgrade/remake of Fantasy Zone II (originally a Master System-only release).
I found holding the system was pretty quickly fatiguing for my hands, so I got a sort of shell that makes it larger and more ergonomic, which helps. I'm really not a big fan of the circle pad, though... it doesn't feel precise, and the resistance it has doesn't feel too good after a while.
I have a question about it, but if it's something that's outside of the bounds of the forum rules, please delete it. I bought the system used from a US seller and he included an R4 card. Is that something that you could use to install emulators?