For quality and the number of sizes of bits that are available, the Brownell's Magna-Tip is the best.
These are a true professional quality set, made of the finest materials.
The bits are deliberately made hard so usually the bit will break, not an expensive and hard to get gun screw.
An advantage is, if you break or damage a bit, all you have to do is email Brownell's and they'll send you a new bit free.
I recommend buying a set with the Law Enforcement size handle. This is the perfect size for good control.
The standard handle is too big, and the stubby is too short.