ZEC. Compare against any of the Nvidia cards in the GTX 1070 to GTX 1080 ti range - on both "power efficient" and on "max hashrate".
AMD cards are ALMOST getting competative there again - but even with RX 570 cards in the $209 range they still have a bit to go to manage it.
To be fair, go ahead and include the "return" figures for the AMD card doing ETH vs the NVidia card doing ZEC, as that is probably going to be the "best option" for each card.
Don't forget to factor in SYSTEM COST - the AMD card might be half the price, but you also need to add in the "cost per slot" of the system itself on each side, which will be the same.
It's a more fair comparison to compare a common 6 card RIG of each card involved, since cards don't mine by themselves.
Thank you QuintLeo for the insight, so here are the #s for all of us to review, critisize and learn what is the most profitable GPU\Coin to mine for x amount of $ invested:
Pre-assumptions:
1) Since we assume that we will build two SIMILAR rigs, each accommodating 8 GPUs, this means that the common expenses of each GPU will be the same, meaning that one Nvidia GPU will need for example extra 10$ to be functionally mining and the same goes for one AMD GPU. Therefore, this will leave us focused on the cost of the GPU, Electricity draw, and $s generated at the end of the day\week\month
2) Lets assume that the cost of electricity is 0.11$ per K\W. If it is a bit different this will affect both cards and not one of them
Lets start with the Nvidia cards:
1) ASUS Dual GeForce GTX 1070 OC, DUAL-GTX1070-O8G
This card costs 406 EUR in Europe, this is the lowest price possible here for this card
The hash rates ranges from 420 to 480, so I picked up somewhere in the middle 450
Power draw ranges from 120 to 140, so I left it at 120 K\W
The results are 2.62$ net profit per day
If we divide 2.62$ by 406 EUR we get 0.0065$ return on each invested EUR
Now lets compare this with AMD RX 580 card:
1) AMD Sapphire RX 580 Nitro Video Card + 8GB
This card costs only 291 EUR here in Europe
The hash rate can get easily stable at 29 MH/s mining ETH
It can also dual mine DCR at 900 MH\s without impacting the hashrate of ETH
This will draw below 130 W, but to be on the safe side I use 130 W
The result is 2.48$ a day (net)
2.48$ divided by 291 EUR initial cost of GPU, will leave us with 0.0085 $ return on each invested EUR
0.0085 - 0.0065 = 0.002
0.002 divided by 0.0065 is 31% higher return from AMD compared to Nvidia
Please correct any mistakes i have made in the above calculations, also please feel free to correct them and present your own calculations, i will be very glad to point out what i think you have missed from AMD side
Sorry for the long post, but it had to be this way, if we are going to dig into deep details
I hope that this benefits everyone...