I'd vote Bad Axe 2. From what I've been reading of people's experience, it's generally accepted as the most stable board - and stability was my first priority over all else.
That, plus the Asus name seems to have taken a sudden plunge downwards from what it used to be. I've been reading a lot more incompatibilty complaints with Asus boards than Intel's, and don't even get me started on the "Striker" strikeout. Yes, Asus does put out a lot of Bios updates on certain boards...but how many of those updates are to FIX previous problems that never should have been there in the first place? Not a bash against Asus - just an awareness. Considering just how many different motherboards and versions of each motherboard they offer, some things are bound to be missed. I still think it's a high quality company.
Having said that, I'm sure either board will be fine. Those were the 2 boards I was looking the most at when looking at 975. You might want to throw Abit's latest 975 "MAX" in your research too.
As for overclocking concerns, while it's true that Intel's boards could not keep up in the past, this does not appear to be true with the Bad Axe 2. The current record over at XtremeSystems with the X6800 chip is the Intel Bad Axe at over 5.5Ghz. (http://www.iamxtreme.net/coolaler/WR/x6800/wr_1m_5526_9000S_cpuz)
Most people seem to "easily" reach 3.6Ghz on a 6600 with air on the Bad Axe 2, so I wouldn't consider oc'ing a weakpoint. I fully expect to reach 3.6 on my 6600 BX2 when I want to, but I'll be keeping it at stock for the next month or so. I also don't think the Asus should have any "problems" reaching that speed either.
The best thing about it from what I've been reading on this and other sites is that while the Bad Axe 2 overclocks great, it's "stable" when doing so.
But honestly, whether it's the Intel, Asus or Abit - you'll be getting a very good board any way you slice it. None of them would be a mistake, and I don't think any of them are "clear cut" winners in any category. If you want built in Wi-Fi (which is nice, but I heard isn't too good compared to external routers) - the Asus would be the better choice.
I hear all 3 boards raved about often, but I've rarely ever seen someone complain about their Bad Axe 2. Can't say the same for the others.