Weigh whatever factors you personally consider important (e.g., price, max aperture, image quality, etc.)

If you are shooting with a 1.6 crop factor then the 24-XX might not be wide enough. I've used the 24-70 on my 20D and I definitely didn't like that it wasn't wide but it's a beautiful lens. I also have the 17-40 and it's a great lens on a 1.6x or a full frame.

I can't figure out why he's asking.

but I'm curious which one everybody would pick for their individual shooting style, budget, etc. This isn't a poll for a personal purchase.

Of course if I had a 5D I would have the 24-70.

For me the 24-105 is the ultimate walk around lens. I have trouble deciding which of the three too mount when I go walk through the city to shoot. It's also a great lens in the studio where strobes negate F/4. The trio gets me a pretty wide swatch of focal lengths with only a very minor gap. If I add more glass it'll probably be a 50 1.4 or the 85/L for low light.

and would have picked up the 10-22 for real wide stuff. that being said, i love my 17-40

17-40 on the 20D and 24-70 on the 5D. I like to shoot wide angle so I need to have the short focal length in there. Both of them are great lenses. I'm sure the 24-105 is a nice piece of glass too but I just wanted to get a faster lens and I also love shooting wide open.

I often have hard time deciding between the 24-105 and the 70-200, so I usually end up using both of them. 24-105 is a great walk-around lens, I love it. I also have the 50 1.4 but I don't use it much anymore.

<ul><li><a href="http://www.the-digital-picture.com/Reviews/Canon-EF-24-105mm-f-4-L-IS-USM-Lens-Review.aspx">link</a></li></ul>

But owning a fair number of them, I'm really glad I've got the 17-40 in the mix. Don't have a higher-end zoom of the 24-70 or 24-105 variety, but the 24-70 is damn tempting. I keep looking for decent used ones at my local camera shop.

and has a different purpose, you cant really compare them like that

f2.8 is nice, but most of my shooting is in daylight. None of those lenses are long enough for fast actions sports anyway. You're in the general all-purpose, walk around and portrait range there. I chose the 24-105 because it had the widest range and IS.

The 17-40 is very popular, but I think that's only so because it's inexpensive L glass. It's neither wide enough to be your only wide-angle, nor long enough to be your only lens for walk-around.

My current setup:
Tokina 12-24mm f/4
24-104 f/4L IS
100-400 f/4-5.6L IS
50mm f/1.8
100mm f/2.8 macro

I lack a good low-light sports lens like the 70-200 2.8. So I'll add that someday. I'd also like a nice fast wide angle zoom like the 16-35 f/2.8L for indoor party type shooting like weddings and such. But I'm not sure that's great bang for the buck.

24-70 and 24-105 are different lenses... The 24-70 is faster, and slightly sharper the the 24-105.

24-105 does however make a better all around..

17-40 is a completely different lens.

granted, you can probably reduce it down to just two (17-40 + either 24-70 or 24-105).

on a 1.6x body (20d/30d,rebel), i find the 24-* too wide to be usable for wider angle shots, though on a 1.3x body (1d mkII), you can get by in many situations without needing a wider lens.

one thing to remember about the 24-70 is that due to its weight, on a 20d/30d/5d/rebel body without the battery grip/vertical shutter installed, it will feel lopsided (front heavy). not so w/the 24-105 (i've got both of them).<ul><li><a href="http://forums.audiworld.com/photo/msgs/11926.phtml">24-70 vs 24-105 i posted from a couple months back</a></li></ul>