I would also like to understand the issue about power phases on the board. The gigabyte has 4 where as the msi has 6. What does this mean ? Is more better, do you usually look for a board with higher power phase design and how do you judge ?
Also one last question on the quality of the boards in terms of mosfets, vrm and caps. Gigabyte uses the term ultra durable 5 where as MSI military class 4. Is this just marketing hype or are the components the same ?
Gigabyte use more copper than other manufacturers. This is probably the reason that Gigabyte MBs are more reliable especially compared with MSI. Stick with asus, asrock and gigabyte MBs. Most others are problematic. MSI is famous for this as well as compatibility issues with memory and GPUs.
Both boards have the same 8-pin ATX 12V power connector and the usual 24-pin ATX main power connector too, so I'm not sure what you mean by different power phases here. Can you provide a link. I'd like to look at the info you are talking about.
There's about 33 boards reviewed here, on many of the boards the reviewer comments on the power phases "The board has an 8-phase power supply, and since it's an Ultra Durable 5 Plus board it has PowIRstage chips."
Just glancing at the GA-Z87-D3HP info, they have added a separate digital power supply chip that handles more amps for overclocking. Great if you want to OC the CPU. Less likely to burn out the components on the MB when OCing the CPU with better heat dissipation.