As a guy that does custom tilling, I have went through a LOT of tines over the years, and I can tell you "for sure" that IS a difference in quality of "some" of the brands of tines.
The problem is, I can't tell you what brands to stay away from, as I buy mine from the same place all the time, and he doesn't handle any poor quality tines. All I buy are Howard tines, as I've seen what "other" guys have to deal with buying cheapo tines.
I do know the Amish here bought some cheep tines that ended up being made in china, the tines ended up being absolutely junk, and the Amish guys ended up buying Howard tines to cure the problem.
I've never bought a "set" of tines, I replace as needed and that's been the most economical way for me, for my tillers...
SR