I'm looking at buying a Phantom 4. I recently took some images on a friend's Phantom 3 to check the quality of the still images, and found a fair bit of noise in the shadows. Does anyone have experience with the Phantom 3 and 4 and can comment if the 4's camera is better with respect to noise?
Thanks.

If you are getting noise in the imagres, then it is very likely your shots are either under-exposed or taken under conditions with too little light. Both cameras produce similar images, the only advantage the P4 has is a somewhat better lens. Feed the camera light - it loves it.

I have had a break of about 6 months from flying my P3P, as I have a new camera giving me 50 MP and I was expecting the images from the Phantom to be somewhat lacking, but just had a week on the Jurasic coast, where the view from 400 ft above the sea, eclipsed anything I could capture from standing on terra firma.  
If you get a bit of noise in the shadows, Lightroom can easily reduce this to minimal.  But the more light the better in my experience.