ETH, Monero, Zcash in that order on 470 4g stock clocks with 1500 straps.
I think monero is a winner because of the low power consumption but it is cold as balls so the extra heat isn't a problem. Depends also on your gpu arrangement as well to which coin is the best to mine, for YOU.
All coins are in toilet
zcash has the same power consumption per gpu and etheruem also, so no monero is not the best anymore in consumption terms, also it's not on par with profit with the other two...
sigh, here we go
Currents numbers for 470 1500 straps stock clocks from whattomine
Zcash 205 h/s = 88 cents day
Monero 640 h/s = 90 cents day
ETH 25 mh = 97 cents day
Monero is definitely low watts on older gpu, for example 290s. Im not sure about the rx cards perhaps it is the same but at least with xmr the coin doesn't tank every single day.