i think there are some pros and cons for both (at least hat i can think of).. depending on how close you want to be to the subject being photographed, the extra tele on the 24-105 would be nice, in order to be non intrusive to those in the wedding.. however, at the longer length, shooting at slower shutter speeds becomes an issue (especially if you are indoors with only f/4).. however, i do own the 105 and my indoor shots have improved (no flash) over using the 17-40 due to the IS.. the 2.8 will allow for faster shutter speeds and will attract more attention to your subjects..
i do notice you have the 100mm f/2.8, so after this wedding, you might not need the added length
i think the 24-105 is a sweet lens, it stays on my camera for about 80 percent of my shots.. i think if i had the 24-70 it would come off more often for the 70-200 f/4 (which by the way is soon being replaced by the f/2.8).. i do wish i had a 2.8 zoom lens..
i cant really speak about quality comparison, but i do know the 105 is superb and id imagine the 70 is no less..
In my photography I ususally want the deeper depth of field that f/4 (or smaller size aperture) will give me (with the exception of portraits), and I sometimes use my tri/monopod or 12' pole (handheld) as a boom, so the IS of my 24-105 comes in handy, as it does for half-second flash photos. One of the advantages of the f/2.8 is that it should have an easier (faster?) autofocus no matter what f-stop you use.
I LOVE my 24-105mm. It's almost ALWAYS on my camera. As Glenn says, it's a great 'walk-around' lens, especially on a camera with a full size sensor.
Well I think my mind is made up and Im leaning towards the
Canon EF 24-70mm f/2.8L USM I cant see buying a ef-s lens
incase I go full frame and I gotta have the f/2.8L
Guess Im gonna have to step back a little and hope theres enough room
Scott A Williams - Roseto, PA
Canon EF 100-400 F/4.5-5.6L IS, Canon EF 100 F/2.8 Macro, Canon EF 24-70 f/2.8L, 580EX Speedlite, Paintshop pro X