NOTE: I've owned both phones. Currently using the V20. The S7 and S7 Edge has a better camera overall. The camera focuses much faster and the low light shots are much better. However, when you zoom in closely on a photo, you'll notice a loss in detail due to the 12MP camera. The V20 shoots much better when there is natural lighting (just like a DSLR) but is terrible at low light shots and can't focus as fast as the S7. However, the detail is much more crisp and clean. So it really depends on the lighting and situation, but the S7 is a better overall well rounder and the Samsung camera software is much more easier to use. However, the benifits and features of the V20 outweighs the S7 so I decided to keep the V20. I can post sample V20 images here if you want.
By the way, you can download the Google Pixel camera apk and use it on the V20. In certain situations, it is better to use that app instead (more simple auto mode).