I have both the FX 70-300 VR and the DX 70-300 AF-P . I also own a 300mm F4 VR PF, a much more expensive (and prime lens) and a 200 -500 f5.6. I also got a lot of great pictures with the FX 70-300. It's quite sharp up to about 240mm. However, as 300mm is approached this lens is notably soft. By comparison, the much newer technology DX AF-P 70-300 VR is not only sharper at the long end, the VR is more effective, it focuses faster, and it is much lighter in weight. In addition you can buy one for about $150 gray market, which is a bargain (In my opinion the non VR model is all but useless and Nikon should be ashamed to package it in kits). Nowadays I only use the AF-P model on my D7100 and am very happy with it, except for serious bird photography where I use the 300mm f4 or the 200-500 f5.6. My FX 70 - 300 is hardly used at all, and only with an FX camera.

In short, for DX buy the DX AF-P 70 - 300 and NOT the FX 70-300. The even newer FX AF-P 70 -300 is a better lens than either of the other 70 -300 lenses but it costs $750. When your budget allows, you can get that one, but for now the DX AF-P 70 - 300 is the one to get.