The Les Paul's 60's neck caters more to those who are used to thin necks, or those who prefers comfort and ease. Its "taper" feature allows better fret coverage as you move down the neck, where the neck gets slightly thinner.
I would prefer the rounder 50's neck profile though, as it brings out the characteristic and the chunky feel of the Les Paul. I would wanna FEEL a Les Paul in my hands. :wink: