I had the 28 - 300 with my 10D and was disappointed so I sold it.  Lost out
badly. Now have some L series and non L series and wouldn't go back to non
canon lenses except for a few specific lens that seem to get rave reviews
(Tamron 90mm being one).  But many will disagree

regards

Don

My advice is to stay away from the Tamron like the plague.
I have one and it has possibly the worst build quality of any lens I have
owned in over 45 yrs of photography.  The warranty service is terrible
(particularly through their Canadian distributor) and the parent company
(Tamron Japan or Tamron USA) has no control over their distributors.
Stick with the Canon and you can't go wrong.
Bob

You are comparing a Yugo (Tamron) to a Lexus (Canon).  

*********************************************************

"I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated."

                             -James Nachtwey-
                        http://www.jamesnachtwey.com/

The Canon.  However, I would avoid getting any lens, regardless of
manufacturer, with such an extreme zoom range.  The image quality, in
general, is usually poor at the ends of the range and only acceptable in
the middle.  Better to get two lenses.  Yes, more money, but
you'll get better quality images.

My rule of thumb with zooms: To maintain optimum image quality never
get a lens with a range more than about 3X.  Less is okay.  Actually, it's
better.  So, with a starting focal length of 28, the max should be around
85.  Up to 105 would be okay, too, but no more.

So, in your case, I would get two lenses:  a 28 to 85 or 105; and a 100 to
300.

Stefan

Oh, it's exactly the same. That's why the Tamron is cheaper. Canon is
just screwing you.