Try this, take a KUB, any one of it, whatever batch u like. When
the bus stops at a traffic light, or a bus stop, lean with your
head against the window and feel the vibration. Now, after you have
done that, try it on a Citaro.
It's not the price of the bus, not the age of the bus, but its
tiny details like this that makes a passenger more comfortable and
less pissed-off when you take a 1 hour journey to and fro every
day.
Not to mention, the KUB's radiator is so annoyingly loud that it
makes people have to talk louder when making a phone call in the
bus.
i believe small details like this, will make people's daily
commute much more bearable and comfortable.
This argument won't cut any ice with me.
You know why?
Its just a friggin bus.
Get over it.
And the KUB is comfortable.
You just have to lower your expectations.
I take 3 hours of bus rides each day, 3/4 of the time on KUBs
and have adjusted well to it and found its plus points good
enough.
And why in the world do you want to lean your head against the
window for??? Its little details LIKE THIS (the oily stains) that
PISS ME OFF to no end. Just imagine having to stare out of
oil-smudged window for 3hrs. 
Bottomline: There's 1100 KUBs, you cannot escape la. And do your
part in being considerate to other commuters. That's more
useful!