I've written a little on why I think automation will always win out here. I'll be the first to admit, I do a great job, but in the back of my mind, I know I can't hold that profile true and keep all of the other constants (translation speed, pressure, and RPM) like a well-engineered machine does.
And for sure, a huge part is convenience. I can run out to my garage and start up my Blackstone, or I can just pop my skates in while I pack up my bag to go in the basement and do no work at all. So, not only can it beat me on some performance aspects, but it's the same argument for using a Keurig versus brewing a pot of coffee for one cup.
I think anyone in this thread who has significant experience sharpening skates manually will tell you it's going to take years to perfect your craft and run into all the issues and know how to troubleshoot them. So if you're down for learning a new hobby, go for manual, just be sure you know what you're getting yourself into. The cost of the traditional grinding wheels (if that's all you're going to look at) will probably work out better financially in the long term. Sparx will always be ~$1 a sharpening after the initial payoff. I bet a traditional stone works out to be pennies per sharpening.