I'd put up an M14 against an early M16 any day. I remember the early M16 with the wimpy barrel was very inaccurate if fired using the sling as we were taught in USMC rifle training. The tension would bend the freaking barrel enough to make it impossible to find a zero. The Marines did manage to get the M16A2 barrel strengthened as well as give it decent sights. I think I noticed all the target M16 derivatives have floating barrels now as well.
I liked my HBAR very much, it was a very accurate rifle, regardless of the stopping power. My Mini-14 on the other hand was useless beyong 50yds, but was a cool little rifle.
It would be more accurate to say that the modern, ultra-accurate AR-15's have a "free floating handguard" -- the barrel was never supported by the handguard, as we'd think of in a conventional stock in a conventional rifle (OK, let's use the M-14/M-1A as an example). The handguard was the mounting point for the sling on the M-16/AR-15, and when using said rifle with a sling in proper rifleman form, the sling is pulling the barrel off-center, since the only other point of support for the barrel is the receiver.
The issue of the handguard/barrel interaction is yet another problem with the M-16/M-4/AR-15.