With all the bells n whistles that come along with 1660 Super, the end of the performance is inferior to a 1070 Ti. However, you will end up paying more for a 1070 Ti, how much are you getting it for?
I am myself gaming on 1660 super on a 1080p res and I find it adequate, so my suggestion is to go for 1070 Ti if your budget allows or stick to 1660 Super and it will still solve your purpose.
But the best option is to wait for a month.. let the RTX 3070 and Big Navi cards launch and that will lead to prices of these cards to go down and you can get a sweeter deal. Also, the market will be flooded by really good second-hand cards within the warranty period