The 24-120mm f/4 was the kit lens that came with my D750. I have no complaints about it. It's compact and has a good focal range. The images it produces have no real flaws that are created by the lens.
But I do not have any experience with the old version. Is it worth upgrading? I have no way to answer that. But I can say the f/4 stands as a decent lens.
My current FX lens selection is Sigma 20mm f/1.4, Nikon 24-120mm f/4, Tamron 90mm f/2.8, Sigma 150-600mm f/5.6-6.3, and recently added a first series Nikkor 70-200mm f/2.8G VR. The 70-200mm was my way to fill that gap between the 24-120mm and 150-600mm lenses. I like to have overlap in focal coverage and less lens swapping.