One thing nobody mentioned is that the ASUS has 16 phase power (12 for CPU, 4 for iGPU) while the Gigabyte has 12 phase power (presumably 8 CPU, 4 GPU).
The UD5H also has power/reset/cmos buttons on the board itself if that sort of thing is of any use to you.
Honestly while I prefer ASUS boards myself I really don't think you can go wrong with either of them.
I was going to mention the phase-power design. Last year's Z68 offering had some midrange to "deluxe" P8Z68 boards with the same (or nearly) phase-power design as the flagship Maximus. The Maximus IV Extreme Z had little plastic cups on it and voltage leads, so you could test voltages easily with a multimeter without struggling to assure contact.
If I were building an Ivy Bridge (or Sandy) this year, I'd get a Z77 board. I've favored ASUS (mostly) for the last nine years, but the board-makers struggle every year to release winners, knowing whatever they know about the competition.
It is extremely likely I would pick an ASUS Z77 board under that scenario. I've browsed the P8Z77(. . ) offerings, the Sabertooth and the Maximus V's. What I usually do, though, is run a search for reviews of particular boards, especially from testing-lab sites like Tom's or X-bit or Tech-Report. Then I run a search for forum reviews from all over the world if they pop up. I start comparing their results and look for signs on forums that this or that isn't working properly or that BIOS revisions are sorely needed. And without a doubt, I start comparing "feature descriptions and specifications" between boards in the same price ranges. I even study the customer-reviews: If a board has ten or twenty reviews at the Egg just after initial release, I look at the 1, 2, and 3-star ratings to see if if the "Cons" are based on some real short-coming, or if there's some peculiar situation that caused problems, or the reviewers were just eggplant newbies who just didn't know what they were doing or talking about. I look at the frequency-counts of reviews-- which tells me what's popular even for a trade-off between price and features.
With last year's Z68 releases, Gigabyte just didn't fare too well among per some exchanges I had here at Anandtech. AsRock boards were touted as outstanding and quickly garnered advocates, but as I understand, AsRock is an ASUS susidiary.
There's always a chance some outfit like eVGA or Gigabyte will score some kudos in every successive annual round of board releases. I've hardly even looked at eVGA boards recently, but I had a 780i board and it is still running tip-top. They had a "Classified" line they released for socket 1366.
A lot of Senior Maestro Guru Masters here at Anandtech forums are using ASUS boards this last couple years. I may not be one of the Anandtech Illuminati or I'm exaggerating this assertion, but I did my homework on the last go-around. I'm absolutely sure of it.
