ASRock has Turbo Boost (MSI Doesn't)
MSI has mini PCI slot(ASRock Doesn't)
ASRock has D-sub+DVI and MSI has DVI-I
MSI has DisplayPort(ASRock Doesn't)
ASRock has TPM header and Chassis fan connector (MSI Doesn't)
MSI has serial port and CMOS jumper (ASRock Doesn't)
This is what I saw different between the two.
Personally I would go MSI because it is a brand that I trust and that has treated me well.