There is no logic in comparing nvidia current generation cards with different AMD cards?
In which case why are you comparing some current nvidia cards, with some old Nvidia cards, and an old AMD card? Isn't that just as illogical?
My stated comparisons offer people the chance to compare performance and efficiency when trying to normalize as many variables as possible. And until Vega is released one will always have to accept some variables wont match.
One can easily see that Vega will be approximately twice Polaris but limited to under 300w. The one has to estimate the architectural improvements and add that on top. Similarly, Vega will have similar numbers of GCN cores as FuryX, but should be clocked 50% higher and again we have to add the architecture gains. The architecture improvements are unknown but we could guess 50-70% based on history. SO we could take an RX480/Rx580 and increase performance by 50% for the same power draw, scale up performance with the additonal GCN cores and finally scale to around 250-275w. Doing this we see performance should be well between the 1080 to 1080ti at least
Comparing to a 1070 or a 980ti doesn't tell you as much information. Vega isn't competing with the 980ti or 1070, but the 1080 and 1080ti. You could do somethign weird like estimate the 1080 performance form the 1070 but why bother when we know the 1080 performance?