There's a lot of hate around for WarZ and for good reason(see WarZ thread), but I don't think having a poll on a forum is going to give you your answer. You need to try them both really.
I've tried both and in their current states I much preferred WarZ. I found it a more polished experience(being an actual game helped). DayZ took me a while to setup, took a while to find a decent server(the server lists are a mess), the controls are terrible, the UI is terrible, the graphics look dated and the style is very bland/generic. There's a pretty steep learning curve and you'll have to spend a fair bit of time being frustrated before finding your feet.
WarZ is a stand alone game and feels more polished. It lacks the depth of DayZ but its much more accessible, with better controls and UI. Biggest problem with WarZ is the support surrounding the game and its future. But you can read all about that in the WarZ thread.
End of the day, imo both games will give you very similar experiences. It all hinges on the DayZ standalone really. If this makes DayZ more accessible and a more polished package then it might be the one to go for.
