The problem with topics like this is that people talk about it without understanding the fundamental issues of weapons design.
The design of all long guns require compromises to bring together two lines as closely as possible - your line of sight and the bore line of sight.
The bore line of sight goes from the barrel through the chamber through the bolt through the stock and should ideally form a straight line to minimize muzzle movement due to recoil. Most modern assault rifles, especially western ones such AR-15 derived designs has a straight line from the barrel through the stock into the shoulder.
On the other hand, by the time the bore sight line reaches the shoulder on these early model AK and M14, they are well above the stock.
Check out how much drop there is in the stock of early lever action rifles:
What this means is that the recoil doesn't go directly back into the shooter's shoulder, but introduces torque that forces the muzzle upwards. The further the drop from the boreline, the more torque and muzzle rise there will be due to the moment arm being longer. This is bad for a number of obvious and not so obvious reasons.
Second thing to notice about the differences between rifles with a lot of drop at the stock is that the sights are closer to the barrel. The ones with bore lines that go straight the stock have to elevate sights off of the barrel. This is also not a good thing. The further the sights are off the bore line, the greater the bore angle is off the line of sight, creating a higher parabolic path for the bullet trajectory, which alters the drop table and where the crossovers are on your zero:
Take this exaggerated example: Let's say I had a pistol and my target is five meters away at eye level. If my pistol is at eye level, then my aim is pretty much horizontal. OTOH, if I am firing my pistol cowboy action style, from the hip, I am aiming my pistol at a significant upwards angle to hit that eye level target. Similarly, the farther off the bore your sights are, the more rise and fall are being introduced to bullet trajectory (generally speaking, the flatter the trajectory, the better - the ideal bullet would be completely flat and travel in a straight line.)
Ultimately, you want minimum distance between the sights and the bore, while limiting stock drop. These two things are mutually incompatible, so by compromise the head comes down to establish a cheek weld on the stock to bring your eye in line with the sights.
A lot of competitive shotgunners prefer a more heads up shooting position but this can effect your speed for rapid followups shots because you are making more adjustments for muzzle movement between shots.
If you want to take a look at a modern long arm with ergonomic sights, look at the Steyr AUG A2's original offset sights:
