I vote for the f4L 24-105 IS. The only problem I see with your crop sensor Canon would be that it's effectively 35-120 and you may want a wider angle. FF it's perfect.
A key, IMHO, to total happiness with zoom lenses, even Canon's L-series, is software that adjusts for the lens-specific errors in the lens. As you go wide, in particular, this lens has a lot more distortion than a prime lens a the same focal length. However, with a software like DxO's Optics Pro, you get increase sharpness and geometric corrections at EVERY focal length and aperture. It's amazing. I carry the 24-105 and the f4L 70-200 IS and a 25mm extension tube and feel like I have the equivalent of a suitcase full of prime lenses.
I should say that I'm using these lenses with a 5D MkII, so I have the added advantage of super high-ISO performance. The noise level at ISO 3200 is probably superior to your older Canon at ISO 800. I'm not dissing the older camera, but just saying that f4 is plenty of speed for the 5D2, but it might not be enough for others, depending on the subjects that you shoot and how much you use flash. Having useable ISO of 3200 changes your whole outlook on available light photography will be altered. So, subject to this caveat, the f4s may or may not work for you.