From an owner of an OLED deck that I've used almost everyday for the past year on a plethora of games, I would recommend going for the lower end Go S steam version (if you're going for the budget route).
The OLED is showing it's age even with lesser demanding games since older games still update their graphics and such over time. Unless you're going to solely use it for 2D platformer style games. The LCD deck is a slightly less powerful version.
I'm holding out for the Go 2 and hoping there's official steamos support.
I've been watching him for a while now for his Souls-like playlists. He doesn't really like playing Assassin's Creed type games but he'll do it out of popularity. Funny that this is the game he's going viral for.