Quite a few variables depending on your electricity costs and card availability.
ETH still profitable, but I wouldn't invest in new hardware to mine it at this point. Few other coins like Zcash and Monero as well. Also with the Claymore miner, dual mining can be more profitable (ETH + Dcred)
Nvidia cards are more power efficient per hashrate, AMD mid end cards hash higher per card cost.
ETH uses the memory more than the core. In fact, single mining with ETH, the core is so underutilized, it can be underclocked quite a bit (-100 to -200) and power dialed back to 65% without impacting mining hashrate.
For ETH, GDDR5 memory timings are perfect and that's why 1060, 1070 and 1080ti cards get sucked up quickly, driving prices higher. GDDR5X doesn't work as well. There are tweaks, but not enough to justify paying more for less hashrate than the 1070's.