Having played with both M-16s and M-14s in Nam I’d say that it’s a choice depending on needs. If you are is a position where you have to hump ammo around in a pack you’d be better off with 5.56 because you can carry twice as much. If you have a defensive mode or some sort of vehicular support for easy resupply then 7.62 would be preferable.
Being a civilian now I’m happy because I can use my 30.06.
Until my boating accident, I had a M1 Garand, M1903A3, M1 Carbine and a M1A. Love them all. Have an AR that I don’t shoot much, but I used to carry a M4 in full auto as a duty weapon that I really liked too. Really like the 30 caliber though. Accurate and certainly does the job it’s designed to do.