At 500 yards 5.56 has less energy than 9mm muzzle energy, and has severe bullet drop, necessitating very accurate estimation of range in order to have your bullets not hit the ground in front of your target or sail overhead.
Yes, better optics, but also bigger, higher velocity ammo for long-range engagements.
“At 500 yards 5.56 has less energy than 9mm muzzle energy, and has severe bullet drop,”
Elevation changes in MOA at 600 yards are about the same as 7.62 NATO. 17 minutes up from a 100 yard zero.