[cockerpunk]

what are you trying to drill through?

generally machine tools follow a trend of more and more hard, but as the hardness goes up, they get more and more brittle.

you need the hardness to cut harder and harder metals/materials, but you have to be very careful of cutting deflection, because they get more and more brittle.

generally, coatings are used to reduce friction, and heat, not really help with the cutting itself.

generally, unless you are cutting something exotic or hardened steel, i'd stick with high speed steel with a titanium coating (the gold stuff)