Any site not using ES chips. Sites with ES chips are development/testing partners with specific board companies, and truly are highly biased. That's why they have ES chips in the first place. Site like TPU with retail chips had to get them through alternate means, like myself, I had to wait until just before the launch when Intel was shipping out retail chips before I got the two I have now.
In the end, bias like this isn't really a big deal, you just need to know where that bias comes from, and where it's directed to. I'd suggest Anandtech as the singular review site with ES chips that is NOT biased when it comes to motherboards...they are just biased towards Intel a bit, and that's no secret.
I have several boards here that OEMs asked me what I wanted, and now I see what I wanted directly in these products. Either they gave me what I want, or what I asked for many others were asking for as well. That said, there are clear and obvious design choices to me that reflect this with every board...like each brand went to sites like here, asked reviewers what they wanted, and then made a product directed at that site's traffic.
When I report stuff to OEMs, I report what you guys tell me, with my own "technical" spin added on to justify why you guys want those changes. So there is no "Best Board for Intel Z87"....there are many many fantastic boards, each that are designed to meet the needs of specific users. The board that is good for you, probably won't be good for everyone. The crowd here does seem to be astute enough to understand that just simply stuffing features on a board till it's got no room for anything else isn't really much special...which makes most high-end boards that some may say are the "best", not the best, here.
The MSI Z87-GD65 GAMING is very perfectly targeted at the audience here, and does significantly meet the needs of most Z87 users. It clocks well, has decent performance, and is relatively light on the wallet. Is it the best board ever? Nope. I have changed how I do my scoring this round, and the MSI Z87-GD65 got a 9.0 and Editor's choice award. It didn't get a 10/10.