Depends completely on application. Do you need extreme reach? Because a .50 at close range will draw fire like fresh turds draw flies. But asking your 5.56 to connect at 1500m is like wishing for your enemy to be struck by lightning.
Is it a TEOTWAWKI situation and it'll be defensive sniping?
A municipal police situation where the likelyhood of a shot over 100m aproaches zero?
"Those who have long enjoyed privileges as we enjoy, forget, in time, that men have died to win them."
Franklin D. Roosvelt