Tottaly agree with the posts about Linux's use of memory & it's management. My Ubuntu system utilises my 8GB of RAM (kernel option) better than my Windows system..
However.. with Android I find "killing" some processes that are in the background (apps that you want to close as you are no longer using them) sometimes slow down the phone. Or be it 'seem to' slow down the system.
So as soon as I kill the unwanted processes the phone seems to be faster..
Just like on a PC..killing a process will free up memory..but as you've pointed out Linux's memory management means unused memory is somewhat wasted..