Depends at what price you can get em really. 570s are ridiculously overpriced like the 580s most of the time. Fortunately you can get those overpriced cards for less than some 1070s. Unfortunately for folks like me I prefer to pay in BTC on Newegg for GPUs and they sell out in minutes.
I was lucky to get gigabyte 570 4g for 184$ each on newegg and pushed them to 29Mh/s
but what about 1060/1070 hashrate ?