Luval said:
it a big differeent you are talking about.. I am not base on "impression"
use before both lens before. and I couldnt agree more that the Af of Tokina is faster and more consistent . Talk about f2.8. and Tokina is always a 2nd choice to a Nikon for me .
its not clear which mount he is talking about.. i cant speak for the tokina/nikon connection as i use a canon.
i bought the tamron in the end and can vouch for it. and it is also a 2.8.
AF speed may be important to some.. may depend on camera etc.. for me, picture quality is the key defining criteria as i dont take much action photography.
of course, the best thing is to take both lenses and try..
but sometimes, people dont have that luxury or opportunity. and in this respect, all we can depend on are independent reviews. and the reviews of the tamron are solid across the board.
see
http://www.the-digital-picture.com/Reviews/Tamron-28-75mm-F-2.8-XR-Di-Lens-Review.aspx
see also
http://www.fredmiranda.com/reviews/showproduct.php?product=187&sort=7&thecat=29
(and in that forum, there are some who have also compared against the tokina and sigma equivalents)
finally,a head to head comparison in popphoto.
http://www.popphoto.com/assets/download/8212003124116.pdf
http://www.popphoto.com/assets/download/572003105657.pdf
as you can see, the tamron shows better quality across the board at all focal lengths.
again, before you jump down my throat, dont misunderstand me. im not saying go out and buy the tamron.. was just pointing out that there are similarly priced lenses out there that he should also consider.