The high tech bits I save for high tech metals. I have the better "Drill Doctor" to sharpen my non coated, old fashioned bits. Broke or dull I fix-um. Does an anti-walk split back cut tip too. It has paid for itself many times over, and I will buy one again immediately if it dies.
Number and letter sets together as one, are my preference. Though really large, actually often a bang for the buck. I normally check with a local contractor/industrial supply houses(heat&AC, plumbing, electric, etc), Grainger, or even Harbor Freight for deals on machining stuff, rather than the local big box hardware.
