Both lenses are on Bryan's general lensrecomendations list. I have the Tamron and think it is excellent for the price. I have never used the canon 17-40 but considering it is an 'L' series it is probably worth the extra. If you ever upgrade to a full frame like the 5D you will not be able to use the Tamron but will the canon. Both are a little too wide for my taste but that's just me.


Mark