Originally posted by jmarkku @westmill: the Tamron is a bit "loose" compared to the Sigma, which is a solid brick. Considering the original idea of having a versatile landscape and street lens, I sure would recommend the focal range around 15mm to 60mm.
I have the Tamron lens. I could not describe it as loose. Its fairly well built. Its certainly old fashioned in its design and very noisy too. It looks like it outperforms the sigma wide open too. The sigma does look a good deal. I doubt the OP would regret going with either of these. Ive not read the full review but it looks a good improvement from the previous offering. The Tamron has just one flaw.... it suffers rather badly at 17mm setting with a field curvature. Despite the MTF showing great results at F2.8 you need to stop down all the way to F8. I find this not a huge problem in the field as you genraly tend to stop down at this focal lengh anyway. The sigma does look very nicely built though. HSM is certainly a bonus too. Either would do me