Ups, you changed your question? That makes people, who answered before look like they canīt read. 😎
Now the answer has to be different, because we are talking about different systems, and not updates of rather similar cameras. If you can afford it, take the D750.
I agree with what mark is saying, but at the end of the day, the bigger the sensor the better still applies, although the overall difference in picture quality between crop and full frame isnīt that big today, as it used to be.