IMO they are quite similar. Since you mention holiday do remember that LG selfie quality isnt as good as competitor brands, if that is a point u need to take note of
The V20 may be a little bit better than the G6 in image quality cos right now G6 still has oversharpening issues (and V20 main sensor is bigger), but the G6 wide angle is very likely better than the C20
Battery wise definitely G6 better, however I always believe that u can carry a powerbank if your phone need more power, but if your camera is less good, nothing on earth that you plug into that USB port will improve the camera quality, so dont worry too much about battery and focus on camera performance