I think a determening factor could be less in the boards overclockability, and perhaps more in it's functions and price.
Like, if I'm going to install WinXP or a 32 bit version of vista, having 3 ramslots is more then sufficient (3GB).
If I want a server, install a 64 bit os, 6 slots (12-24GB) is rather a must.
I probably won't use a server to play games, though some people might.
Also pricepoint is a good factor to determine which board could be a snatch.
Quality of capacitors and boardmaterial, as well as longetivity of hardware play a role in making one board win over another.
There's no winner when a certain board manufacturer has increased performance for lower power, but when their boards die within their first year of use due to the use of bad components!