Well, obviously the 1070 ti is significantly more capable than the 1660 Super, and Colorful is a fairly old school, trustworthy AIB partner, so if you can get customer service for Colorful products in your region that that is easily the better choice. If you can't get service, then go with the Zotac, because while the Zotac is less powerful, it is a good choice as well.
Are these new or used? What resolution are you planning to game at?