I understood the difference when i was working recently on data analysis. I had to do 23119x350 ols regression in matlab and computer saves the parameter and some other values which are structures, as computer save these values during computation, they save it in a temporary memory, which is cache memory. If i can finish my work i can just save all variables in my harddisk and clear cache memory. But unfortunately i couldn't when i arrived 4500th line, the computer was out of cache memory. It took more than 3h to arrive 4500th line.
That amounts to say, if the computer is working very long without stopping, it saves works in cache memory. I am not specialist but it seems that even you are doing heavy video editing, you won't be out of memory because i guess that a video editing operation won't take 3h (?i no idea), but if yes, you will need high cache memory.
I ordered my 17 mbp with 2.2 because i know that i was doing this kind of work for my master thesis and i won't do so big computation for my other works. however keep in mind also that the fact that it was out of memory is because of structure of variables, you can easily create a real matrix of that size using very little memory.
i hope that it's clear now
