Do a search and you'll get answers quicker. This has been hashed over and over. Everyone has their own opinions so you'll get lots of different answers. Some are Winners Choice, Muzzy, Zebra, custom made ones, etc. All will have differences and claims (price and durability are probrably the two major ones). I usually post www.bcyfibers.com if you want to check out differences in materials used. Good luck.
Winners Choice are nice strings and frankly I think some pro shop made strings are as good and a lot cheaper. My customers seem to think the ones I make are good.