The small n3DS is my favorite. I got mine in 2015, with the Happy Home Academy bundle. I've since gotten a bunch of faceplates for it, plus solid/translucent ones I can further customize with stickers. I've enjoyed it thoroughly.
I've also got 2 launch 3DSes (US and Japan), and an n3DSXL. But out of all of them, the small n3DS works best for my hands, including those nice rounded corners. I can even use the
Retro Plate & Watch without losing access to ZL/ZR.