Okay then, humour me by explaining in plain, simple English how having 4 cores makes any of those processes faster or better?
On paper, it sounds quite common-sense : bigger numbers is always more desirable and means better performance, right? However, if it's anything I have learnt from using Apple products, it's that numbers in a vacuum don't always tell the whole story.
With your Facebook example, I would probably be better off with a faster (but still single-core) processor, better internet connection and arguably a better designed native app optimized for touch and direct input. But more cores?