I use all three also.
I'll dub right onto the thread for most things, with a few following exceptions...
If I want a shaggy/spiky body and dubbing with material that's tough to dub right onto the thread, I will use a dubbing loop.
If am dubbing something pretty sparse and using something like CDC, I may use the split-thread to help keep the material aligned more neatly.

That's all my brain is going to kick out this early in the morning.