I self- lower most of the time. Fast and easy.
No messing with making a plan A and Plan B with the groundie.
I can adjust the tension in real time to work with my cuts.
Rip cuts and bender-cuts , as appropriate, keep forces on ropes down, and rip cutting is far faster that face- cuts on everything.
Sling and biner or natural-crotch on the piece being lowered for double-whip tackling allows you to use smaller ropes (I rarely pull out one of 6 or 7 double-braid ropes from my truck) and free the rope before the groundie is back from dragging, moving you on to the next rig. Also, midline lowering or using the other end to lower can speed a climber up.
Groundie- catching them, then passing the rope to the climber to lower, frees them up to land the piece of the climber can't land it alone.
The right length lowering line keeps the standing end or of the piece/ landing zone.
Check out Tom Dunlaps O.L.D.S. thread.