I think that they are all made by Lang. Pick whichever color of case strikes you the best or whichever price.
They are the biggest name in this market. If you're going with the Lang/Kastar product, I suggest considering price vs warranty. If you're visited by a Snap On truck, and expect to use them regularly and break them (the taps are breakable, but the dies, not so much), then maybe that's the way to go. For my part, I own the NC and NF Snap On die restoring sets, plus their full range of files (all flea market purchases, so I bought what was available not specifically seeking out a brand), but no restoring taps.
Then again, I can't say I've ever needed thread restoring taps. Thread restoring is about pushing rolled over damaged peaks back into place. That's something that easily happens to male threads (which a die an fix), but not really a problem with female threads. I've had corrosion and crud ****** up female threads, but in that case, a standard tap has always sufficed for me (though that use requires particular care).
After all this, if I just need to fix the mushroomed tip of a bolt (my most common need for fixing a thread), I'll reach for a fine triangle file before anything else. I use these as tools of last resort (along with rounded nut sockets, etc.).
