I've got a SNES mini and a PS Classic.
As everyone has said the main drawback of the SNES mini is the short cable length and the relatively high cost. It is really cool to play Starfox 2 though, no idea why they didn't release it.
The PS classic is a mixed bag. The hardware itself is really good - the attention to detail is even better than the SNES mini. I also love that they used proper USB for the controllers yet they still look like the real thing when plugged in.
The software however...bleh. For some reason they chose some PAL 50Hz games alongside some 60Hz ones. The emulation is also below par, though thankfully it is really easy to hack and it turns out the hardware is more than capable - you can even get it running Dreamcast if you wanted.
Typical Sony really, great hardware and sh*t software
Still, it is hard to knock for the price.
I am also looking at getting the PCE mini, which has gone in an interesting direction. Rather than a regional selection of games, they're offering the same games worldwide and only the hardware design differs.
Although you end up with some untranslated games, I prefer this approach because it avoids a situation like the Mega drive mini where the EU gets (IMO) the worst line-up.