No, the performance is not equal, the 390 outperforms the 970 75-80% of the time. Please look at your sources.
The 390, and 970 are aimed also at 1440p gaming. Most titles stay above 60fps, and even at 1080p, some games go over 3.4 GB of vRAM, and even more at 1440p. Of course, both the 290, and 390 outperform the 970 even more, due to stronger hardware, and better memory.
What type of power bills does your third world have? If a lightbulb is on allllllll day, is about 3-6 cents, but a GPU isn't on max load all day, so by the end of the year, it's $10-20 more for a neet, max.
The a sync is still based off of software, therefore, more work for the CPU, there's no denying that the 1080 is more powerful still, but it's a bit of a disappointment still. It lacks the hardware, so they can show an improvement for the next series of cards to keep sheep buying every generation.
And Nvidia has shit drivers too, look around at Nvidia, not just AMD problems, Nvidia had/has issues with Windows 10, normal blue screens, or just drives that destroy the hardware, take a look at the laptop displays Nvidia drivers destroyed.
I guess you're too much of a fan boy to actually see the facts. You should probably be more unbiased.