[robski]

Hi John

The 24-105L will be much the same zoom range, IS feature and speed you have on your 20D 17-85IS setup. I would expect the L to be sharper and clearer than your current lens. The 24-70L will be better for low light but only zoom slightly beyond a normal lens. So how much do you use the long end of your current zoom ?

I have the 24-70L f2.8 and it is clear and sharp, But like and Christine we have the smaller sensor of the 20D which will use the sweet spot of the lens. Wieght of the f2.8 ? It took a few weeks to get used to it but I think nothing of it now the wrist muscles have built up.

If the above points have not made the decision for you then the issue will be how much difference is there in the edge performance on a full frame sensor. Both of my L lens have given better results than any other lens I have had.

The chances of finding somebody with a full frame Digital and has tried both of these lens is very slim.