COMMIEDOG'S PROFILE

So I've been kicking around the idea of making an RPG in a modern or near-future setting. So far, so boring, right? I've seen and played several amateur RPGs with settings that fit the description. But I've noticed that most if not all such projects create their own worlds, complete with ficticious geography and history, rather than use the one we live in, even though doing that requires creating more a backstory and history for the world. I haven't really decided on whether to do that myself or to try basing my world on the real one.

So this is what I'm wondering: what are the advantages and disadvantages of each approach?