Finally got to try War Z and I really enjoyed it.
They have a slightly different approach at doing things, excellent load times, great inventory system, and the graphics are quite nice (probably bias since I never really enjoyed Arma II's engine). Consistent day and night/time across all servers forcing you to get the night experience. Melee works fantastically, I had no problems killing zombies with a flash light and if you hit them correctly in the head it only took three hits with the hammer. That is probably due to the Oct 31st patch, in which they fixed zombies and melee. I also found aiming a lot more rewarding in war z but that is probably a personal choice since I also like the slower speed at which zombies come at you when compared to Day Z.
What I don't like.
Lack of mic support, hope to see that implemented.
I miss sprinting on top of running that Day z had but like how stamina bar is influenced with how thirsty you are and drinking stuff.
The way zombie detection works right now. I favor Day Z's zombie detection over War Z atm. What I mean by that is detection is less variable in war z than Day z. Not to mention darkness and bushes have no effect on detection but hopefully they change that in future patches.
You are currently not able to drive any cars, but they aim to add that.
No doors for buildings but there are a lot of buildings to go in and out of.
Safe Zone camping but once factions are introduced that should disappear as well.
Both have great potential and having played war z with its expanded map and updates from the oct 31 patch was an overall positive experience and I'm sad my key has expire already. Still waiting to see what both have to offer towards the end of their production before buying either.
Thought I'd chime in on War z.
EDIT: Apparently he apologizes for what he said lol
http://forums.thewarz.com/showthread.php?45103-My-Last-post