I have a lansky diamond, I find it very good, I've had the lansky stone knife sharpener since a kid and it was ok
but for serious knife sharpening this is what I would recommend
when you need to sharpen knives quickly this is the go, it uses sharpening stones and is similar to the lansky how it works just bigger but I made some diamond plates from a bit of timber and cheap diamond coated sharpening plates from ebay, as you can see in the photo
when I am butchering I dont want to have to stuff about sharpening knives and this works a treat