1070 SP Lux = $3.47
580 Dcr+Eth = $3.1
ETH is for a lazy mining, set and forget. And ETH profits now higher than usual due to recent jump in ETH price. Most time of the year it was losing to 1070 more.
With 580 you can always look on more profitable coins on cryptonight algo. With 1070 you need to look to much more algos, and have to change it often to maximize profit.