It is rather strange to talk about the number of programs available on a Mac or Windows platform, as most people do not get any further then using Microsoft Office.
So comparing Macs and Windows PCs is like comparing Mercedes with Cadillac. They are both cars, but you buy a Mercedes or a Cadillac because the differences you like, not because a Cadillac has more roads to drive on.
Hah! True enough, but once Macs build up some wider consumer support, do they really think virus makers and hackers aren't going to focus more on that platform? It's no secret - though it's wisely ignored - that the main reason the Mac is deemed more secure is simply because the market share of the Mac isn't big enough yet for hackers and virus makers to bother focusing on it.
On a side note, there's no apostrophe in PCs and Macs. :)