The diamond sharpener is the perfect tool to give your knife a brand new edge. They are designed to shave away the blade creating new teeth for the blade to use, where as a honing steel realigns the teeth without removing them.
The butcher steel is a maintenance tool and should be used often to keep your knives in great condition. Eventually your knife will not be able to be honed to a usable edge and that’s where the diamond sharpener comes in.
Using your steel is like brushing your teeth, you want to do it often. Sharpening knives is like going to the dentist, you only want to do that once or twice a year.