I'm looking to buy some quality drill bits and was wondering what you guys suggest as far as material is concerned. They will be mostly multi-purpose bits, but I figure if I buy high quality bits intended for drilling metal then they will work on just about everything else. HarborFreight.com has a 115 piece set of Titanium Nitride Coated bits for $39.99. They also offer a 115 piece set of Cobalt bits for $99.00. I assume Cobalt is the way to go in terms of strength, but are they worth 2.5 times as much as the Titanium Nitride bits? Or are both of these sets crap, and I should find another set somewhere else? Thanks.