Several things here.
Originally Posted by kraftman
Ubuntu certainly is a distribution that follows closely the newest software developments. Not only because every six months is taken from Debian sid, but more importantly because the Ubuntu team has a preference for the untested and experimental options. Call it what you like, the point doesn't change.
The benchmarks. Maybe they are not real life situations, as in they're not measuring the cpu load while watching a youtube video and opening this particular pdf file I've been sent today; however, they put numbers to pretty reproducible computing tasks that stress different parts of the system. So, I don't spend the day signing 4096-bit RSA keys, but I surely know I prefer my computer to do it faster rather than slower.
As for the 'proper' kernel config...next time you take a look at a car magazine and see a comparison between two cars, don't forget to complain because they didn't tweak the suspensions or added nitrous oxide to the engine.
PS. In any case, no, I don't think that the kernel configuration has a critical effect in anything regarding performance.