I've had GP32 (BLU), GP2X F100, Wiz, Canoe, PSP, NDSL and Pandora.
The GP32, although a lovely device, just doesn't cut it for emulation of the systems I want. GP2X was very much loved, and still is. Wiz was a pile of barely usable cack. Canoe sits on a shelf gathering dust - and is also not a patch on the GP2X (surprisingly, the GP2X controls are better than the Canoe!). PSP was a pain to get rooted, and has a blurry as hell screen, so sits next to the canoe and GP32. The NDS is wonderful for homebrews and NDS/GBA/GBC/GB games, but for emulation blows donkeys cocks. The Mrs has the NDS now.
So all in all, it would have to be the GP2X. There's just something about it that appeals to me.
D.