I would suggest the 70-200 f/2.8 - but here's why:
A lot of weddings/indoors are subject to low-light and limitations on the use of flash. I was shooting in a conference room once, and my lens would only allow f/5.6 at near 200mm. I couldn't use flash, and had to resort to high ISO. Although the high ISO's in camera's nowadays are pretty good, even then you'll still see the noise and grain and every camera is better at a lower ISO than it's higher ISO.
Believe it or not, sometimes even at ISO 3200 you're not getting enough light with an f/5'ish aperture at high zoom.
In these situations, a zoom lens with a wide aperture such as f/2.8 is a blessing.
If you can't afford the Canon, I would take a look at third party lenses which offer high zooms at f/2.8. Yes I know that some folks will disagree with third party, but if I had to choose between the ability to have 200mm at f/2.8 with a third party lens vs not having that, I would choose the third party. Better something than nothing.
Just my two cents.