Frankly speaking, I find myself use the 28-300 a lot more than my the other 2 zooms in the same range. I know a lot of photogs get those focal lengths in 2 pieces i,e 24-70, 70-200 because they wanted the f2.8 for certain events. Nevertheless, your 24-104 and 70-200 f4 is more like a walk-around lens with the same application as the 28-300.
If you always shoot at wide angle, 28-300 is at f3.5. For landscape you don't really need big aperture. If you shoot more at the longer range, 70-200 f4 is only 1 stop bigger than the 28-300 at f5.6 and you need a TC 1.4 to get that extra range. With digital you can easily cover that with higher ISO, IS etc. If you want to use it for portrait, I think a lot more other lens are better and cheaper.
I've been an advocate for many years of the same idea that Chase jarvis is now promoting which is "the best camera is always the 1 with you." Now we have better quality camera phone, of course that is better than what I have back then. When I first got that lens, I can carry only it plus a lightweight film body knowing that there are no better quality zoom. I always carry a big bag because it looks more natural with my size and the longer lens barrel still fit nicely. Only thing to consider would be the push pull mechanism which some people dun like compare to IF of your the other 2 choices.
Having said that, if your main idea is to walk around to take more photos, general purpose, less bulky, less things to bother, walk, tour and enjoy instead of thinking of your photography needs etc then 28-300 make more sense even though the weight can be an issue for some people.
On the other hand, if you want more assurance - having 2 lenses vs 1 lens in the mist of accident, theft etc, then get the latter.
I trust and love my 28-300 so much that I can just go oversea tour with only this zoom and a body with pop up flash. Note this lens is best for FF format. If yours is cropped sensor than I don't think this zoom works as good anymore. :dunno: