I may end up going with the Gigabyte UD7 for the fact that the Maximus IV puts 2x cards at x8 instead of x16.
I'm probably one of the few persons who've had both boards, a B2 UD7 and currently the Maximus IV Rev 3.0.
Both can do x16 for dual cards, both of them require these cards to be right next to each other in order to enable x16, the only difference is the UD7 requires both upper x16 slots to be populated while the Maximus IV requires the bottom slots and an extra card on the first x8 slot in order to activate x16 with dual cards. That extra card can be any card, a sound card, a RAID controller, an SSD drive, etc.
Trust me, I've tried all configurations and x16 wont offer much improvement over x8, I've seen this with my own eyes. The only problem is having both cards so close together will effectively heat the top card 15~20 degrees higher than the bottom card. I decided to use x8 SLI just because of this, the performance difference is almost non existent.
If you want x16 for dual SLI or X-Fire, you may wanna look at he P8P67 WS Revolution, it offers you a better x16 configuration for dual cards. One advantage the Maximus IV has over the UD7 is that for 3-way SLI you get x8x16x16 on the Asus board vs. x16x8x8 on the UD7, so for triple card setups the Asus board might theoretically be slightly better.
I have mostly used Asus ROG boards, and decided to give the UD7 a try. The board OCs like there's no tomorrow, and the build quality is awesome, but the BIOS is really unstable, and it got really annoying having to flash my BIOS everytime the board crashed just because the Dual-BIOS function activated on any minor crash. I've never had that problem with the Asus board.
As for OCing performance, both boards allowed me to reach over 5Ghz without any issues, but the UD7 allowed me to push my RAM performance a little bit more due to tighter timings on that board, so you could say the UD7 wins by a neglegible margin.
For looks, I think I liked the UD7 better, GB really got his act together for their P67 boards, although the Asus board doesn't look bad by any means. The Maximus IV some more features than the UD7, like Bluetooth, UEFI, and a better software suite IMHO; it also feels more like a luxury board, so I guess you get what you pay for.
Now, having had both boards, I can tell you, from my personal experience I'm not buying a Gigabyte board again. Let me tell you a short story:
After the P67 recall was announced, I called GB and asked them for instructions on how to exchange my board, they told me to return it to the original seller, I felt like GB just let me out there with no support, I contacted ProVantage (the original seller), and it took them ONE FULL MONTH and many phone calls and emails to give me the RMA! all the while GB support told me that since ProVantage was not one of their direct re-sellers, there was nothing they could do... Imagine my dismay.
After finally recieving the RMA autho from ProVantage, (worst support ever, some Reps just straight up hung up the phone on me!
) I shipped my board back and assembled my backup rig. In the meantime, I read all about Asus and MSI offering direct advanced exchange for all their P67 boards, all this while GB hung me up to dry.
I decided to go back to Asus while I waited for my refund from ProVantage, I was one of the lucky ones to be able to order on the first shipment of Rev. 3.0 Maximus IV boards.
Two weeks after I returned my board to ProVantage (and with no refund in sight) I received a call from GB saying that they had changed their mind and were now offering a direct exchange option for their P67 boards, I almost wanted to strangle the person on the other side of the line. I told her all the problems I had dealing with ProVantage, and asked them for their help, the rep basically told me "dude, you're really screwed" (not their words, but you get the message)
It took me over a month to get my money back from ProVantage after they received my board according to UPS, and not before I called my credit card bank and gave them all the shipping information and photos of the board ready to ship and they contacted ProVantage to ask for my money back. That's my personal story, and I'm pretty sure there's ppl who've had a better experience than me with GB, but I'm not ever buying one of their products, trust me, that's not bitterness there, it's just common sense.
So yeah, IMHO the Asus Maximus IV is technically the best board, if only by a small margin; it's also more expensive, but as I said, you get what you pay for, and if that also means getting the best support in the business, then I'm all for it
