Ads are probably the worst way to get this type of unbiassed information...
honestly, it seems kind of silly to go in with the idea that "PCs are better then macs" because your essay itself will be biased; you have to focus on facts, not marketing crap that is designed to sway people in one direction or another.
What I suggest, is learn about the history of PCs in general, including Mac computers; although it's a bit biased itself (to the mac side, it seems) I suggest watching "pirates of the silicon valley" If not for facts but for some insight into the two architectures (or more precisely, the figureheads behind each and their corresponding design goals).
Perhaps make a list of Pros and Cons; nobody can deny that the mac has some pluses itself, (namely, in the beginning it adopted SCSI with open arms, the creation of the Apple Data Bus (LONG before any "standardized" connectors on PC, save Serial Ports which need a *censored*-load of configuration),
perhaps weigh competing models of Apple and PC hardware.