One advantage of a compressed load for an AR or any semi-auto is that you won't have bullets pushed deeper into the case during feeding, which can raise pressure. There is no downside to a compressed load---unless you're trying to pack so much of a slow burning powder under the bullet that the bullet creeps back out of the neck. That can, and DOES happen.
Nothing is wrong with a proper compressed load-It has the advantage of powder not shifting around because case is completely full. But watch for the creepage as stated above.
If you do go with a compressed load try this. Hold a engraver, handheld electric massage or electric shaver to the cartridge or to the cartridge loading tray. The vibration will make the powder settle down in the case. Be careful you will kick some powder out if not careful. Works better than a drop tube.