I look for bits marked "HS" for high speed, usually in a diamond..
afaik high speed steel bits are what you really want and can be sharpened forever with a steady hand and a bench grinder because your not relying on just a coating like in regular bits...
I don't really know anything about the cobalt ones, it says its solid so you will be able to resherpen them, not sure how cobalt compares to HS, or the prices of any of them period really because I just grab whatever cheap ones I can find at sales or whatever marked "HS"..
and to me they are of much greater quality than bits I find that are not marked HS..
and you can get em for pennies because people think used drill bits are trash, even a HS bit that's been broke in half can be reground easily and will work excellent again before another sharpening for longer than the service life on the non HS bits ive come across..
so to me broken/dull/chipped whatever HS drill bits you can find used are the best bang for the buck as long as there is still enough of the fluted shaft to be reground..
and to me it matters not the brand of the bits, if they have a "HS" on them they are good stuff..
flame me if im wrong please but I have 100 or so HS bits that work excellent with a hand grind with probably less than $10 into all of them...
