Wiz has more stuff in total, BUT you might find certain emulators might run certain games faster on the Caanoo or that you prefer using your Caanoo for whatever reason, so it is totally based on your perception. I find that the Caanoo chokes on playing most videos I throw at it, dunno if it's just my luck so far or what, but I found my Wiz to be preferable for movies, although I usually have to reencode to get good performance to quality ratios... (Pandora is my movie player of choice, although the missing tv-out cable still kinda sucks :S)
You can fit all the Caanoo homebrew on a 4GB SD and still have left over space (in my case, Ginge with Payback, some of the Caanoo commercial games and a few small emu's, etc.)
The Wiz on the other hand, I have managed to fill about 12GB of homebrew/phoneme/flash/interpreter games (interpreter games meaning stuff like doom, quake 2, etc.) and a few emulators (8bit systems and older).
Alot of the emulation has overlap, and certain arcade games are better on Caanoo (like marble madness using the g-sensor I guess...)
I haven't gotten around to testing this, but I like the concept of hooking a usb joystick up to the Caanoo and using tv-out for playing with friends... and the wifi support for multiple things seems to be built a little more solidly into the system.
Analog isn't too bad, atleast I prefer it to having the problem of trying to use the wiz almost dpad style buttons to play mario (holding down run and repeatedly hitting jump just seems a little hard on the buttons and my fingers, wrong shape and too close together)
Finally the screen, I LOATHE the Caanoo's half-asses backlighting and extreme brightness (always washed out even on the lowest brightness) where the wiz looks absolutely stunning from any angle and when the screen goes black and I'm in a dark room, the whole room goes pitch black
I'd say, either setup the card so you can use it in both wiz/caanoo or pick your favorite and fill 'er up!