The only reason for a drop tube is if you have more powder than will fit in a case with just the funnel. Meaning if you drop slow into the funnel with a drop tube it somehow is magic (has to be right haha) and allows you to fit more powder in the case than just with a funnel. I've used it on a 30BR and a 6 dasher when I tried running h4350 but otherwise very little reason to run a tube.
The name of the game is you want case fill, so only use a drop tube when you don't have enough case for the powder you are attempting to use.