Which RAM configuration will give better performance in a Intel Z77 Board. 2 x 8GB, or 4 x 4GB?
Both options are fine, you'll notice no performance difference between either option. I will suggest going for 2 x 8GB sticks of RAM, which is the more expensive option. This will allow you to upgrade in the future to 32GB, if that's something you're after.
Performance-wise, you will not see any differences. If you were to end up moving to a quad-channel-based system in the future, all you'd need to go is get another 2 x 8GB sticks and you're ready for quad-channel.