As far as 17-55 vs 24-105L, I've never used the former so I can't speak into it aside from the obvious: 1) the extra FOV gained by the 17-55 helps on a crop body, 2) f2.8. I can only speak from a photography standpoint, though. I have no idea what is common for videographers. I also like to shoot wide so I'm partial to shorter focal lengths.
Given that, IMO, the 24-105L is a pretty good walkabout lens. Sure, you're limited to f4, but overall it's not as bad of a lens as people make it out to be (not necessarily here). It's a very useable, wide focal range while still maintaining a constant aperture. You'll have to take into account the crop factor of your current or upcoming camera body, though. If you ever like to shoot real wide, that may not work to your favor. The lens also has IS, but if you're using a fixed rig or tripod the benefit is negated.
EF-S lenses are not all bad. As already mentioned, the 17-55 gets high praise, as does the 10-22. I still have my Canon XTi and only kept 2 EF-S lenses for it: 10-22 and 85 prime. The latter is also a great, fast (f1.8) lens and a lower-than-L price.
I have a feeling you may find yourself limited by choosing only a single lens, though. Such is the bane of photography...prepare yourself for financial pain.