When you start comparing the list of pros and cons of the Sigma tested here and its immediate rival, the Tamron SP 150–600 mm f/5–6.3 Di VC USD, you find out they are by and large identical. Indeed you deal with almost twins, with the same parameters, price and performance. The differences, if there are any, are slight. For instance the Tamron is sharper at the longer end of the focal scale in the frame centre but the Sigma performs better on the edge of the APS-C sensor and full frame. The Tamron wins when it comes to the correction of vignetting but the blurred areas look nicer in the case of the Sigma. In many categories the rivalry between those two ends in a draw – like for example in the case of chromatic aberration, spherical aberration, distortion, coma, astigmatism and the performance against bright light. The Tamron’s optical stabilization is a tad more efficient but the Sigma offers a better accessory kit.