If you have an old Nikon with unbearable noise at any now common ISO setting, the f/2.8 is useful. If you are one of those who use the non-word "bokeh" in every sentence, you probably want the faster lens—or f/1.4 primes. If you only view photography at 100+% on large monitors, then the 24-70mm probably ignites your jollies more than the superzoom. If you have a lot of money that needs to be spent, and you sneer at anything without a gold-ring, then the 24-70mm is your only choice.
If you are a pragmatic photographer, who shoots for publication, print, or the web with a D3/D700 or better, the 28-300mm is a dream come true. For traveling and working out of a vehicle, I have the 14-24mm and the 28-300mm. I am ready for whatever is around the next bend. I have no problem shooting at f/5.6-f/8.0 for sharpness. My D700 does fine at higher ISO settings. You get a zoom with a 1:10× ratio and it weighs 100g less than the 1:3× ratio of the gold-ring. I have never met a magazine editor or high-rolling client who would reject an image from it. In absolute terms, a gear-head will rant you into the ground comparing the two, but to a working photographer, it simply gets the job done just fine.
