Both are very good pick the one you favor mate i would choose the GIGABYTE GA-Z77X-UD5H because i have not had good luck with msi mobos but doesn't mean that you will so just pick the one you like best
The UD5H is a better bang for your buck. The UDH5 has every bell and whistle for a really good price. It overclocks well, runs cool, and does all this for under $200. It's a very sexy board with the flat black and white. The heat sinks look really good, they are anodized blue with aluminum trim. Looks a lot better in person than from the photos.
That being said I've had 2 that needed to be replaced already for a dead BIOS. I plan on replacing it with a GD65.
I really like the MPower, but having only 6 SATA ports just won't work for me. I know they were trying to keep costs down, but every other board in this class has 8 SATA ports. I would have preferred they skipped the cheap wifi and gave us more SATA ports. You can pick up a really good wifi card for less than what they charge to build it into the board.
Both the MPower and the UD5H have great reviews. If you're more of a gamer, I say you go for the MPower, but if you're a normal gamer, not much of an enthusiast, you'll be more than happy with the UD5H. You could also consider getting The ASUS P8Z77 V-PRO which imo, is better than both of them.