You can't argue with that.
I don't have a 17-55, but I've just bought a 24-105, which won't be suitable for weddings IMO.
As someone already mentioned, f/2.8 is an utter godsend in weddings, and if you are going to use the lens 90% at weddings, then the 17-55 is for you.
Read reviews on image quality, I've heard it's very good.
If you want to use the lens as a multi-purpose one (so travel, etc) then I'd go for the 24-105. I bought this lens for travel purposes.

