Really depends on what you're looking for. Most of these sandbox survivals are in an incomplete state, so a lot of things are subject to change. I suggest getting none of these and holding off until they go gold. The exception is if you have a group of friends to roll with, which alleviates some of the disappointment you'll find yourself dealing with in the games. If you like building, check out Minecraft, especially with mods. If you just want simple survival, try Don't Starve for single player, and DS: Together for multiplayer. For the zombie aspect, definitely look at State of Decay, which is single player.