I am considering getting the i7 4770k + Asus z87 pro mb. If I want to run 16gb ram do I need to get 4 4gb sticks since there are 4 slots or should I get 2 8gb sticks?
2 x 8GB leaves you with two free slots for future expansion so I'd go for the 2 x 8GBkit, I'd only go for the 4 x 4GB kit if it was cheaper (which it likely isn't as it has to go through more testing).
You can run either configuration, but I'd go with 2x8GB RAM
If one breaks, you'll still have one more
Can purchase another 2x8GB in the future if you feel like it
Just get 2x8 since your motherboard supports dual channel RAM.
Edit: doesn't matter that much unless your motherboard supports more then dual channel, otherwise it doesn't matter.