SNES emulation works at almost 100% Frames per Sec on the Wiz, the SNES emulators on the Caanoo will get there, but its a different team of developers working on that one, so its a different emulator (last time I checked).
Also, the last time I checked there was no Amiga emulator ported over to Caanoo but the Wiz has this and it works pretty great.
Personally I don't really think the Wiz or Caanoo are very expensive considering all the things that you can do with them for free.
One major downside to the Wiz is that the OLED screen (while it looks great) has had what seems to be a fairly high rate of failure. Users report that spotting begins developping over time and eventually blocks out the whole screen. However, I've had mine for about 9 months and it shows no sign of this. The Caanoo uses an LCD that is not as 'fragile' and doesn't seem to have this same problem.
SNES emulation on the CAANOO is now on par and in some cases better thanks to a new version of POCKETSNES that came out. The new one is based off of 1.7. I also have a WIZ and DINGOO A320 but my WIZ got the dreaded screen rot. The DINGOO A320 has been getting a lot of native firmware love lately. The C64 emulator is great and POCKETSNES was ported as well. SNES emulation on the DINGOO native OS is really great it even beats SNES9X4D on the Dingux side of things. I love my CAANOO but for some reason I always find myself coming back to the DINGOO. This might change if a decent C64 emu comes out for the CAANOO. The Amiga emu released last month is really nice as well.