Matter of opinion. I've seen better OpenGL performance on Linux on the same hardware, for example, and better filesystem performance too. (I'd also be much less productive without the customizability of Linux window management, but that's getting into more subjective territory).

On Apple hardware? Which?

It was a work-issued Macbook, can't really give you anything more specific than that.

I just put Ubuntu on my 2010 Air and gained battery life and a lot of responsiveness. No driver issues.

Aside, ticks me off to no end that Ubuntu removed the reverse-scrolling option (at least with a desktop) ... On windows, I use an autohotkey script to reverse the scrolling, and for media shortcuts (non-media kb). Ubuntu is the odd one out there for me now.

If you mean "natural scrolling", you can do it at a lower level in linux by remapping the "buttons" with xmodmap. Gnome ignores the system setting for this (or used to, at least; I don't use any Gnome stuff now, so maybe they've fixed it), but pretty much everything else in X will obey those settings.

Yeah, but it was a checkbox option in settings, and not something people trip over... they didn't need to remove it, at least they shouldn't, without another way to do it relatively easily.