Wrong, both are affected but more so the 4gb polaris cards
You're precious 8GB isn't saving you now. 100% wasted money.
Why are you all so obsessed with Ethereum, there is Zcash too which is soaring and I have switched my mining boards from Ethereum to Zcash and I am very happy with such move. Each board have 5 RX 480 Gpu-s from Sapphire with a bit of overclock I am reaching 335 Sols for a card and I making a good amount of money. I don't think this will stop for at least a good few months.
There are alternatives but the simple fact is we need ether and it's millions of dollars of minable currency.
In the future when it is harder to have profit out of ETH then those gpus will flood to other coins.
RX cards will basically be worthless on ETH maybe 6 months out.
It is hard to predict, maybe this will be a bit of a switch to GTX for ether and AMD will sink Zcash profit as users switch over hardware.