Do you need a 70-200mm f4 or 70-200mm f2.8 Lens?

If you're reading this article, then you're probably considering this question in some way or another. It's a confusing question for lots of photographers in the same way that getting a 24-70mm f2.8 or 24-70mm f4 lens is mind-boggling. However, they're perplexing for different reasons. You shoot completely different with these focal lengths. And the prices on both of these types of lenses are a consideration. I mean, if you're a professional photographer, you have to think about how soon you can...