The review was posted on here already. Just getting the word out to those that have not seen it.
The sigma 18-200 is just as good as the sigma 18-125 and better in many aspects. I especially love the minimal vignetting. The sigma has better build quality and even a metal lens mount. It has zoom lock, I dont know if the tamron 18-200 does.
I wish the sigma had the same true focal range that the tamron 18-200. It appears that the 200mm end of the sigma is more like 170mm or so. Or it could be that the tamron 200mm is more like 230mm.
When I get it I will do some testing.
Here are some pics that I borrowed from a Japanese review. Credit goes to them for their hard work.
I labeled and assembled them to illustrate the difference.
Note the sharpness.
Note the chromatic abboration.
This one is at 200mm at f/6.3 and 1/1250