Really nice tablet.
Fast and functional with many features like S-Pen. It lets you write notes with, even if the screen is turned off.
On the screen, Samsung has lowered the resolution since Tab S by about 20%, making the old Tab S from 2014 sharper. On the other hand, the colors are even better on Tab S3 and the tablet now also supports HDR material. The screen is, of course, AMOLED, which means that the answer is total. Once you've started with AMOLED, it's hard to accept the LCD again and its grayish black tint.
A really nice feature Samsung introduced is 4 speakers instead of 2 on a short side. Now you have 2 on both short sides, which means that even if you hold your hands over 1 speaker on each side, you'll hear good stereo sound from the movies. Smart!
Plus for USB-C and fast download!
Carries a star for battery life. Do not count on any 12 hours, as best, you might get an 8-hour screen if you drive the screen at less than half the power and normal use. Not playing thus.
I do not know where Samsung got its 12 hours away, but it sounds like Flight mode and the screen without using the tablet at its lowest power.
At the moment, I do not think there is any other 4: 3 record that can beat Tab S3.
On the other hand, if all the focus is on video consumption, you may be looking for a 16: 9 / 16:10 plate instead. The black edges above and below the film are huge on these 4: 3 plates. Huawei MediaPad M3 8.4 LTE 32GB may be an option, but AMOLED will get rid of it.