Howdy,
When I was in the same situation, I was leaning towards the Wissota but ended up going with the Sparx. The primary driver for this was comparing profiles on new blades vs. ones that had been sharpened for a while. There were drastic differences, and they'd been sharpened by folks that did them every day of the week (local Pure, known for decent sharpening). I figured if decent pros couldn't keep the profile within reason, then there was no way someone like me who would sharpen once or twice a week ever would.
Other than that, the lack of dust everywhere and the "press go and do something else" are also big wins, but they weren't my decision point. The only real downside is that the Sparx is a significantly more complicated machine than a basic manual sharpener, so there's more opportunites to fail and its less likely that you can fix it yourself if the company goes away.
Mark