As to CBN or Diamond, it is decided for your application.
Tormek origional is with diamond wheels. I think that is because diamond wheels can be used for multiple application. But if the end user is specially for knife sharpening, better use CBN wheels. Because CBN is softer, when sharpening knives, it has better finishes than diamond. Becasue diamond leaves deeper scratches. Also CBN works better on HSS or hardened steel, most of knives are made of them.
Our question is if a slow speed wheel in a water bath
Diamond or CBN from Pat we hear the following
Knife grinders use CBN wheels. He has is own “brand” made for him to his speeches by a Chinese manufacturer.
Someone has done a CBN vs diamond wheel comparison and test. According to that test CBN wheels by far outlasted the diamond wheels. The diamond wheels at a certain point start to take extra passes to get the same result as when they’re new; and it gets worse from there. The CBN wheels stayed the same and showed little sign of wearing at that point in the test.