The H-77 and Z75 are very close with features and as you can see seperated by only $5 so they are very similar. Aside from the overclocking abilities which you may or may niot make use of the H-77 baord has 4 sata 6gb/s port and the Z-75 board has 2.
The H-77 board will only support up to 1600mhz ram while the Z-75 board will support up to 2800mhz ram.
So it appears that each board has thier strengths and weakenesses so yuor going to have to look at all the features of each board and make a list of which features you will use on each board and then add them up and the one that you will make use of the most is the winner. The reason for this is because of how close the two boards are.