I went with the 24-70mm for my D610. It's the lens I use the most and sometime it's the only one I take with a 50mm prime.
With the D750, you shouldn't be afraid to increase the ISO. You have much less issue with noise on a full frame camera and 6400 and even higher shouldn't be an issue.
The choice of lens in the end is really dependant on what you are shooting. I mostly shoot urban settings so I feel less need for a powerful zoom.
|