Agreed over the dsi, though I love it. The only exception is if you only play physical media, then the DS lite's ability to play the entire GBA library is pretty cool.

For me it's the fact that I can emulate basically all retro consoles on the n3ds, including imo the best existent way to play VirtualBoy games in actual stereoscopic 3d. That on top of the fact that it's the only way to play 3ds games in the native experience, with 3d, which is impossible on any emulator. Combined with the social features and build quality of the device, and it's unbeatable. Get a USB 3ds charger and it's the perfect travel console. I bring it on every trip and leave it on streetpass mode. Especially for Japan trips, I still to this day pick up new street pass pings, which is so incredibly delightful to find when I get back to the hotel room.

Though I prefer the non xl version, as it's a truly portable console rather than the XL which is huge and heavy in my bag.