I have the Mpower all i can say is its awesome its very nice and clean looking i would post pics but i dont have a gpu for my system yet =/ got my 3570k at 4.5Ghz onit at 1.25v i like this mobo alot and cant do anything other than recomend it =[)
The ASRock one has a fan on it. Small fan = high rpm = noise. Also, you may have a nasty surprise if (or when) tha fan fails.
The ASRock has way to much yellow on it. You will never be able to color coordinate your build (if you're into that sort of thing).
The MPower is cheaper.
I couldn't find any warranty info on the newegg site but I got my MPower with a 5 year warranty. The only other Z77 motherboard with a 5 year warranty (that I could find) is the ASUS Z77 Sabertooth.
All Z77 MPower boards are hand tested with an overclocked CPU with Prime for 24h before leaving the factory.
The MSI board ia avrage proformance...not so good on the overclocking side =/....lacks features compared to the formula....everything else is fine..it looks good tho^^
Asrock OC formula will out proform the msi board both in proformance and feauture...the only downside is the color schem. migh not be some people cup of tea. but its fine for me if its proforms like a beast. also you need to be experienced in overclocking to overclock this board.