R9 270X vs GTX 1060 (or RX 480). How big of an upgrade would it be?

AMD FX-6300 (stock) / 16 GB RAM / R9 270X / display: 1600 x 1200 (4:3)

My friend wants a GTX 1070 but money is tight. How much of an upgrade would either a GTX 1060 or RX 480 be? By far, his most played game is Rust; he has 200 hours played in the last two weeks. He has to play the game on the lowest setting to get respectable frames.
 
Solution
I would get a new CPU first, 6300 will struggle to keep up with those cards.

But if a New CPU is not an option, a 1060 would be a better choice due to the lower CPU overhead needed.

The 2 GPUs would perform closer if paired with an intel cpu, but with an AMD CPU the 1060 would pull ahead

His low performance on Rust is also due to the 6300 having poor single threaded performance and Rust is a CPU intensive title.
I would get a new CPU first, 6300 will struggle to keep up with those cards.

But if a New CPU is not an option, a 1060 would be a better choice due to the lower CPU overhead needed.

The 2 GPUs would perform closer if paired with an intel cpu, but with an AMD CPU the 1060 would pull ahead

His low performance on Rust is also due to the 6300 having poor single threaded performance and Rust is a CPU intensive title.
 
Solution


If he is doing lots of streaming whilst playing games, an i7 would make a world of difference to him.
But for now a 1060 would probably be a good option then can upgrade to a better CPU later down the track.