Prolonged barrel life, more consistent accuracy during longer strings of fire, less deflection, no chance of blowing it up through ridiculous volume of fire... It is, point blank, a better barrel with a more sensible profile. The drawback is the additional 4 ounces of weight right above your support hand; this does shift the rifle's balance slightly towards the receiver, though, so the weight difference is a wash.
IME, a lighter rifle is almost always more accurate than a heavier rifle when both are shot offhand, regardless of which is mechanically more accurate, at least within reason. Less muscle fatigue means the nut behind the trigger stays tight for a bit longer; and the primary variable in accuracy is the shooter, not the weapon.
Now, in my ever-so-humble opinion... Go for a KMR/MCMR Mk2 upper with an ELW barrel and an ambi charging handle. BCM CL barrels aren't known for being precision rigs, so going for a heavier barrel when you don't plan on doing a clone, mag dumps, or F/A seems unnecessary, since the additional weight won't benefit you as a shooter. The ELW is superior to the classic M4 profile while being lighter, with a better point of balance near the receiver, rather than out at the muzzle. Going from an M4 clone to a modern LW recce build is night and day, the reduction in weight is a tangible benefit that you will feel the moment you pick it up.