The drop tube is more consistent and efficient: I have tried both ways, side by side, and the drop tubed loads settle deeper, at a more consistent depth. I have also tried holding my loads atop my vibrating case cleaner for a few seconds. The drop tube loads still work better. Consistency is everything in accurate BP loading. Gravity is constant, the 24" tube is always 24".
Also, dropping the powder allows fines dust to drift and settle on top of the load. Settling the powder by vibration brings this dust down to the primer, making for inconsistent ignition.
However, for CAS loading, or most open sight hunting, as has been said, you can dispense with some of this. I don't drop tube revolver loads, and the wad isn't needed for those applications. But when the load gets past 40 grains, I drop tube, and if the range is greater than 100 yards, I add the wads.