Why I selected it?
1. Any super zoom is a compromize. The 28-300mm lens give better
range, but at aparture of 6.3, that can cause problems with the
camera auto focus. The difference between 200mm and 300mm is not
that large, and on a DRebel sensore the 200mm is equivalent to
320mm anyway.
The Tokina gives also the 24mm. Those 4 extra mm is a large number
in WA.
2. Review at
http://www.photozone.de:
Tokina 3.5-5.6 24-200mm - rating 3.2
Sigma 3.5-5.6 28-200mm - rating 2.84
Sigma 3.5-6.3 28-300mm -rating 2.30
Tamron 3.5-6.3 28-300mm - raing 2.65
Tamron 3.8-5.6 28-200mm - raing 2.63
Review at
http://www.photographyreview.com
Tokina 24-200mm - rating 4.21 (39 reviews)
Sigma 28-200mm - rating 3.95 (42 reviews)
Sigma 28-300mm - rating 4 (20 reviews)
Tamron 28-200mm - rating 4.1 (39 reviews)
Tamron 28-300mm - rating 3.7 (53 reviews)
3. Here are some examples from this lens:
http://forums.dpreview.com/forums/read.asp?forum=1029&message=10923769
Another example (with a Hoya +2 macro lens):
I have to pick an all purpose lens from one of these two Sigmas.
Does anyone have any advice or experience with either of these two?
Could it be there is a compromise with the 300 in quality because
it's range is so broader?
1. 28-200mm F3.5-5.6 ASPHERICAL MACRO
http://www.sigma-photo.com/html/pages/28_200CHZ.htm
2. 28-300mm f3.5-6.3 Macro
http://www.sigma-photo.com/html/pages/28_300_macro.htm