Depends on your hands and screen size preference
As a person who owned and OG 3DS, New 3DS XL, and now a New 3DS, the New 3DS is the best one. Slightly larger screen along with the faceplates? Too cool!
Also the 3DS XL screens, while bigger, don't really do the resolution any favors.
That's just preferences though. They're all good. Even the most recent New 2DS XL looks to be great.