can i give explanation plox
the HK416 shouldn't even be in this lineup because it's just an AR15 that has a gas piston mechanism (short piston specifically) instead of direct impingement to make the gun cycle so it can fire with every pull of the trigger (full auto branches off of this by loving with the trigger mechanism but let's not get into that).
basically an HK416 or any other piston AR15 has a literal piston thingy right above the barrel that is hit by gases and pushes back into the working parts of the gun by rotating the bolt and blah blah blah. the same exact mechanism is in the AK74 and AK100 series, even the AK103/104). on the contrary the AK47 uses a long piston mechanism. there's really no difference.
on the contrary a "direct impingement" rifle such as the AR15 and its derivatives literally use the gases directly to operate the bolt without using any piston or anything. these are where reliability issues arise because of temperature, fouling, etc.
what I'm guessing is that the feel of the weapon and its mechanical attributes will lie on the end user to decide what they like better when it comes down to piston mechanism weapons.
thus, a more sensical battle would be between, if we count the HK416 in, that rifle with a 16" barrel vs. the AK-101 with its rounds per minute on par with the former because AK-type weapons usually fire slower, not that it really matters.