Upload & Sell: Off
Myabe someone with more experience can chime in but I'll spill my take
I've used my 24-120 f4 on my d800 and I must say I'm very very happy with it. It's plenty sharp to the corners, vignettes a bit, lovely colours, distorts a bit on the wide end, but superb glass nonetheless.
I tried a 24-70 a bit but it was too heavy, just goes to 70 and too expensive to justify it. I didn't have a chance to pixel peer it too much though.
I believe the difference of those 2 lenses is not the optical quality since both are great, but rather, do you need f2.8 or not? I believe that is what you have to answer yourself.