I have the Tamron before and feels that it has a slight edge in build over the Sigma.
Also Tamron comes with 3 years warrenty.
In terms of picture quality both are neck to neck and don't expect too much on a super zoom.
me have a 18-70 D70s kit lens. what is the differences or the pro sand cons between sigma and tamron 18-200?
Mmmm Tamron mount is not all plastic, it is a hybrid with metal inside and engineering plastic outside. Somehow I feel the mounting for Tamron is smoother.
Actually is is still better to go for the Nikon 18-200 if you are using Nikon camera.
I'm using a Sigma 18-200
the reason of choosing the Sigma over the Tamron is a build quality. Tamron has a plastic mounting while the Sigma has a metal one and Sigma feels rather Solid to me.
But Given a Choice...I would have taken the Nikkor 18-200mm VR