VRS Design sent me final production cases for the Samsung Galaxy S8 and S8+. With these, I was able to compare the exact size of the new S8/S8+ in comparison to LG G6 and LG V20.
The Galaxy S8 will be slightly taller (or same height) and slimmer than the LG G6 with slightly higher aspect ratio (of 18.5:9 we suspect). The Galaxy S8+ will be much taller (around 3/4 inch) and slightly fatter/wider than the LG G6. Compared to a standard 5.7″ device like the LG V20, the S8+ is slightly taller and slightly narrower, meaning you will have much larger 6.2″ screen that actually will feel much smaller than traditional 5.7″ devices.