hey people, I tot of getting a 70-200 f2.8 lenses for my D600. I m looking at nikon, tamron n sigma. of coz I know nikon is the best choice apart frm the pricing. wat abt tamron n sigma? I did Google for the reviews on both 3rd party lenses but it getting me confuse. would like to know did anyone try both lenses before? any reviews or advise frm anyone here in clubsnap. tks.