rust or dayz

At least for now, DayZ. Rust seems like it's going to be a lot more fun!...But not now.

There is actually no way that the final version of the Rust gonna be better than the final version of Dayz.
And regarding to the early access option, you just play it for the fun bugs, discovering the game, some learning, or just simply because you are a huge fan of the game (concept).

Rust

Dayz because in my opinion you are able to find more items in dayz + third person view.
it depends on what you like.