Refresh features include:
OLED
HDR
90 hz
Better battery life (50wh vs 40wh)
Cooler
Lighter
Even better performance, even though not advertised by Valve! (because of the better DDR memory 6400mt/s vs 55000mt/s)
Bigger screen
Digital Foundry review:
https://www.youtube.com/watch?v=Z1KLj06fn2s&t