The only competition is in terms of time and money you want to put into it, and... IDK man buy whichever one you're more excited about first, buy the other when you have money and time to play it. /shurg Hell, wait long enough and you might even get it on sale.

TBH, I think at least part of it is the tendency for companies to exploit human nature for profit; it's not necessarily a gaming community thing as it is a "tribalism is a convenient way to establish and maintain a consumer base, and it's been ingrained to the point it crops up even when the publishers/companies in question aren't actively cultivating it," thing.