Its a pretty tough choice; the PSP for all its age and warts is a pretty good kit, even today. Certainly there are some good titles on it, and the PS1 emulation is pretty tops. So don't get rid of the PSP (I didn't
That said, the Pandora and Wiz do a very good job with nes, snes, gba, genesis, and even ps1; N64 is pretty wonky on PSP due to PSP limits, but is pretty good (for some games at least) on Pandora.
The Caanoo doesn't have much for it yet(its brand new!), but assuming it picks up the Wiz and gp2x heritage it will have very good emus for nes, snes, gba, genesis and probably even ps1 (though I wouldn't know.) I doubt n64 will be useful on caanoo.
Caanoo/Wiz and Pandora overlap at the emus, and both have good controls for such things (noting the different ergonomics.. clamshell versus candybar style devices); The pandora has more tech in it (faster cpu, larger screen res, more general capabilities, keyboard, etc), but you have to examine your price points and interests. Do you want a more general device (thats a little larger and pricier) that is great at gaming, or do you want a device that is only good at sed gaming, but is a little smaller, etc?
Caanoo is excellent (it really is, I just got one, and it _feels_ damned fine), and Pandora is excellent (much more capable a device really); Wiz is excellent (more or less similar to Caanoo spec wise, but tinier and the older model; I'd take a Caanoo unless pocketability is a concern, Caanoo is slightly smaller than a PSP, but Wiz is like a GBA Micro more or less.)
It is a tough choice my friend
But it depends.. if you plan to be carrying something around in your pocket all day and need it in tight spaces? do you want to use it for wifi web browsing or AIM or the like? watch high def movies or not?..
jeff