When I PP the images they get better. Because I shoot Pentax and wanted a 70-200 2.8 solution, my only options were the Tamron or Sigma. The Sigma has the HSM (hyper-sonic motor) which works very well for sporting events. Optically, from what I read, they were similar, so the HSM was the deciding factor for me. I am not as hung-up as some others are on OEM lenses. I will use/purchase what I need and can afford and if it happens to be a third party lens, so be it. Some others will only purchase OEM lenses and that is fine. Maybe their budget is greater than mine, but I have not been unhappy with my third party lenses.