both are equally useless and wastes of money imho.
if you have a braided cord on the mouse you should be fine just letting it dangle off the back of your desk over any other cables.
the only cases where such products might be useful are:
-desk is abrasive or tacky which causes mouse cable to stick
-there is something big in front of your mousepad
-you have a rubber non braided cord which sticks on everything.
if you absolutely must have one, a mouse bungee is going to be more useful as it sits back off your mousepad instead of being in the way. still overpriced and useless but better than the armadillo.