The longer title-
Sigma 18-300mm f/3.5-6.3 DC MACRO OS HSM Contemporary
Tamron 16-300mm f/3.5-6.3 Di II VC PZD MACRO
These two APS-C lenses give you an equivalent range of 28mm to 480mm!! A huge range and this I am calling this
The battle of convenience. Two Super Zoom lenses face off!
I am generally not a fan of do-it-all lenses. Lenses that cover this much range make sacrifices in quality - sharpness, distortion, chromatic aberration but when I reviewed the newer Tamron 16-300 a few months ago I was pleasantly surprised by its performance - Yes it still has issues but held up quite well and I certainly do enjoy the convenience, especially when traveling or hiking, carrying just one lens that provides me with a huge range, decent macro capabilities and image stabilization for handheld video. And then Sigma released an 18-300 and I have been asked repeatedly to compare these two lenses. Bottom line about these lenses in general- These lenses are for someone who is happy with the quality of the kit lenses that camera with their camera but wants more zoom and doesn't want to switch lenses.These lenses are not for someone who is going to shoot in low light or wants the sharpest image quality. Personally I suggest you carry one of these do it all lenses and a small prime like the 24 or 35. This is a compromise to the carry-only-one-lens philosophy but gives you an excellent low light sharp lens option when you really need it and does it without adding much bulk and weight to your camera bag.Now let's get to answering the question which of these two lenses is better?I will give you the answer up front and tell you that 9 out of 10 times I would pick the Tamron over the Sigma despite the Sigma being marginally sharper at some focal lengths. Why? The Tamron has faster focusing, full time manual focus and weather sealed as well as a nicer focusing indicator and starting just a little wider.