The main problem with a Chef's Choice (and systems like the Edge Pro) is that while it may be able to sharpen the edge, it cannot thin behind the edge and alter the basic geometry of the knife. And geometry is what cuts. Sharpening removes steel, and over time as you sharpen at the same angle, the knife will become chunkier and chunkier behind the cutting edge. And while you might be able to get the cutting bevel cleanly apexed and sharp, it won't cut well if the knife is thick behind that edge -- especially if you're cutting dense items like carrots or potatoes. So while these sharpening systems might be good for maintaining or sharpening an edge, you can't use them to maintain the the geometry of the blade and optimize cutting performance. Jon Broida, sharpening guru and owner of Japanese Knife Imports, gives a good overview of thinning in this helpful video:
