In Newegg for the comparison chart just click on the compare button thats below the product that's listed when you search in categories. You'll see almost at the top of the page a box that fills up with the product you just checked, you can compare up to 5 products at a time. Once you've selected them all just click on the compare button beside the 5 products and you'll get that chart.
I am not really sure what the reason is for the popularity of the UD4 board. One reason could be the support for SLI if people are set on buying an Nvidia card. I didn't get the board as cheap as you did but it may have come to the same with the combo offer Newegg has with the i5 2500K + P67 UD3 for $320 + Civilization V for free.
As far as overclocking goes, I think the UD3 offers a really good range of options, I'm sure it must be very close to the BIOS options as the UD4 for OC. I'm not a serious overclocker but with the BIOS settings offered here it's given me tons and tons of things to explore. I found a fairly good guide on OC the Sandy Bridge CPUs and have followed most of the steps. It also helps when they explain what each step does so that makes it easier to experiment.
http://www.techreaction.net/2011/01/04/3-step-overclocking-guide-%E2%80%93-sandy-bridge-v0-1beta/I'm upto 4.2 Ghz on the OC with very decent mid 30s C temp on stock cooler. I'm planning to get the Hyper 212+ soon and once I upgrade the BIOS to a full version of F6 I'll experiment more.
As I explore more and read across forums of many manufacturers I see many higher end mobos that seem to be having issues. Of course my view may be skewed as an owner of a lower end board. I'm glad with the choice I made so far and hopefully things do stay stable and that this build lasts me a very long time.
My SSD purchase was the only component I splurged on without doing adequate research though I'm very happy with the purchase. I didn't think much about it when I chose to buy it other than it supporting SATA III. I figured if I'm buying a board with SATA 6Gbps support I might as well take advantage of it now rather than later.
I got the Crucial 64 GB RealSSD C300. After I bought it the price went up by $20 so I sorta saved some money on it in a way. As you'll see in the previous pages in this thread I had to do some searching for an alternate driver for optimal performance.
The default drivers by Win 7 'msahci' didn't give the smoothest of functionality. Once I got the Intel RST drivers the ratings went up, the drive seemed to work much smoother. Before, the drive would stutter whenever there was a write being performed. I thought it was normal but then it got annoying. Things are a lot better now and have never had the stutter after installing the Intel drivers.
Good luck with your build Soar and post away once it's all built.