>not very representative clip

I chose the clip based on what Dark_Shikari (x264 developer) had to say about it[1]:

It shouldn't bias too heavily towards any one encoder like many of the other standard test clips will:

a. It's relatively high motion, so it won't bias heavily against encoders without B-frames or qpel (as, say, mobcal does).

b. It's not so high motion that it would cripple video formats that don't support motion vectors longer than 16 pixels (e.g. Theora).

c. It's not something that benefits an unreasonably large amount from some of x264's algorithms (which is why I picked this and not parkrun).

[1] http://forum.doom9.org/showthread.php?t=154430

I could have done multiple test encodes, sure, but the problem in this case was that downloading several gigabytes of raw source material isn't exactly instant. And even if I tested with multiple clips, I doubt the conclusion would be that much different.

Agreed, a single video is not very representative and the results are still subjective. I would have liked these claims to be backed up by measurements like PSNR or VQM over multiple sources.