I have compared the Sigma 18-250, the Tamron 18-270 PZD and the Canon 18-200.
Have photographed with my EOS 600D with every object the same motives, compared the photos and some properties such as quality, weight, handling and so on.
Purchased from before I have the Canon 18-200, which will probably surprise some here. But now to my notice.
The Sigma lens is processed Meier opinion about "cheap". Feels more like plastic and weighs 600g good. The photos no matter what focal length was not really bad. But if we compare with the other two lenses there has clearly lost the Sigma. As I said, my personal opinion.
So the image quality convinced me the Canon and the Tamron more.
The Tamron object is about 100g lighter. This is of course just traveling just a tad bit better. But when Tamron bothered me even in the normal run the lens "slipped out".
Clear all have a lock switch but this was the Tamron really more than disturbing.
The Canon lens weighs approx 600g but feels a little better. The quality has convinced me. Negative course that the Canon was not a lens hood while.
In any case, all travel zoom lenses pros and cons.
For me, anyway.
Sigma
-600g
-something 'cheap' acting
+ Priced at best
+ Lens Hood
Tamron
-Rutscht Easier out
-70 Expensive than Sigma
+ Ca 100g lighter
+ Lens Hood
Canon
-no Gegenlichtblende
-600g
+ Optical and handling of her very good quality
+ 200mm + 250mm or difference between 270mm little difference
So my decision was between Tamron and Canon with me that Canon has convinced the pictures made before me.
I kan anyone to do give the lenses with each other to compare. Time rumhören if someone from the friend or acquaintance of these lenses has.
I hope I could help a little when buying