Sigh. I'm tired.
I will concede that my judgment was based on previous NVENC performance (which as the article states was horrible), but even today, if you check the tables just below your quotes, you'll see QuickSync is twice as fast for about the same quality (Core i7 3770K vs GTX 680).
The question is: is it desirable to have QuickSync on Linux or is it irrelevant [even today that Nvidia has got its act together]? That depends on how much free time you have. I have very little. I applaud QuickSync is finally coming to Linux.