I've no experience with the 24-85/2.8-4.
The 24-85/3.5-4.5G is a sweet lens. Too bad it's a G. It's sharp and lightweight.
The 24-120/3.5-5.6 is a fantastic lens for the money. A bit slow on the long end... but reasonable in size and weight. It does have fairly high distortion, which makes it unsuitable for certain types of photography (e.g. architecture)... but I find it to be a nice walking-around lens.