I think the horizontal flat glass disc things are Worksharp products. I know lots of woodworkers like them.
https://www.worksharptools.com/woodworking-tool-sharpener-ws-3000.html
I don't care for sandpaper-based abrasives. Sandpaper is for large objects where you have to bring the abrasive to the item (like a body shop, or when finishing large pieces of wood or such). When you can bring the metal to the abrasive because it's a small workpiece, there are definitely better options than sandpaper.
IMO, over time the consumable expenses for a belt or paper based sharpener will add up and eventually overwhelm the price of even a very expensive Tormek.
A selling point for me on the Tormek was that the high purchase price buys you low residual costs. The Tormek wheels last a LONG time. The Japanese waterstone is unlikely to be worn appreciably in my lifetime or 3 more lifetimes. The standard stone is known to last a long time even in professional full-time shops where it's doing dozens of knives a day. The Tormek will run a decade with just electricity and stropping paste.
One could eschew the standard Tormek wheel and go with a multiwheel strategy using diamond and Waterstone, and you'd basically never have to buy another wheel. Leather strop wheels are cheap and last a long time too.
I have the Worksharp Knife and Tool sharpener-- the one that looks like a mini slack belt grinder. I would get about two knives from a fine belt and it's be totally loaded. Since these belts are over a buck each, this thing would break me over the coming years buying consumables for it. And then there's the need to buy these special belts. What if Worksharp goes under and you can't get more belts? It's one thing to use a "standard" belt like a 1x42 or a 2x72. But these little guys that are proprietary? I'm not a fan of proprietary or single-source items, I see that as risky.
I'd be more inclined to buy a bunch of 1x42 belt sanders for HF or Grizzly and setup the varying grits on those. A 1x42 belt is under $3 in most cases and lasts a LOT longer than a little worksharp belt, while also working much faster.
Or go with something like this:
https://sharpeningmadeeasy.com/belt.htm
In all those cases, though, the belt systems can remove a LOT of metal very quickly. This would allow a pro to work quickly. But it also means the margin for error is very, very slim.
I think a lot of people don't realize just how hot you can get the very edge of a blade with standard power sharpening methods. The apex is going to be around 0.1 microns thick. That's a ten thousandth of a millimeter, folks. You won't see it turn blue, but it can get super hot and you'll never know it because only the tiniest metal at the very tip gets hot and loses temper. The rest of the blade is so much more massive you'll never feel it. You could have the very apex flash to 600-700F and blade in hand will barely feel warm.
Grind a really thin piece of steel on the bench grinder and notice how that very end is glowing red hot even when you can still hold the piece with your bare hand. That same dynamic is playing out on a smaller scale with almost any powered dry sharpener.
Hence, I believe the slow wet action of the Tormek is the way to go for anything you really care about.
