Check out this video 6:14 and about 9:50 in:
https://www.youtube.com/watch?v=X_Hbms_e_bc
Rotating the long piece of chenille between rubber legs is way easier and faster with rotary and you don't break the flash chenille fibers off like if you tie it in traditionally.
Another example similar operation made easier is a long rope of dubbing - it's so much easier to "feed" a 6 inch rope of dubbing into rotary action than either (i) make giant wraps around the hook (you probably know what I'm talking about) or (ii) do multiple dubbing "additions" in steps of 2-3 shorter dubbing ropes, which is way less efficient since you pick up and put down the dubbing instead of doing it in one go.
Same with wire bodies like for a Copper John. Feeing an 8" piece of wire in rotary mode is simple you don't need to make giant helicopter wraps around the hook.
You can also rapidly orient the fly to tie it upside down while maintaining the same hook shank orientation (regal will angle the hook oblique to horizontal, since not true rotary) which makes it easier to miss the hook point when wrapping down the bend or on a curved shank hook, or tie in a parachute. If you don't think so try it you will be surprised.
The list of possibilities are pretty endless with some ingenuity you can do some great stuff. Check out this video for palmering hackle and tying it off in one operation. Check out 4:34 into the video. Brilliant.
https://www.youtube.com/watch?v=-rX8hxV_Eik
-John
