Telephoto-zoom Lens Comparison - Canon 70-300mm F4-5.6L vs. The Alternatives

I'm sure some of you are debating whether you should buy the Canon EF 70-300mm f/4-5.6L IS USM Lens (~$1500), or the Sigma 70-300mm f/4-5.6 DG OS (~$600). The third option is to buy the Canon EF 70-300mm f/4-5.6 IS USM (~$650). Well, as you can see, there are three 70-300mm quality lenses. Before we continue, let's throw the Sigma 70-200mm F2.8 EX DG APO Macro HSM II (~$1200) and Canon EF 70-