My personnal fave design would be the GBA SP
I loved that little bugger, was comfortable to play on for long times, when folded closed it was the PERFECT size to just put in a pocket and forget about.
Thought about buying another, as even though the 3DS is close its a bit to big to just easily stuff in a pocket and forget about for me.
To me it either has to be small enough like an SP that it can go in a pocket and be forgotten about, or big enough that you can sit on a couch and play it but not feel gimped by a small screen. The normal 3DS falls right inbetween those two for me which is why im not keen on it and have an XL. But woud rather have a 3DS that is the same size as the GBA SP
The best way to find out if you can trust somebody is to trust them.
Ernest Hemmingway