The Snap-on sets are just rebranded Hanson. They are made from carbon steel. That is an acceptable set for occasional use. If you need to cut numerous threads, consider high speed steel taps and dies. Greenfield, Morse and OSG are just a few of the better brands.
Also, ditch the POS T-handle tap wrenches that are included in the typical set, and replace them with some from General Tools. They cost only about $15 each and are far superior. Don't bother wasting your money on ratcheting tap wrenches - in most cases they typically aren't more efficient.