When I bought a secondhand Honda 435 straight shaft, it had a well-used butterfly head. I've continued to use it, often in punishing conditions and I found it to be great. Cutting with 4 strands of cord really works a treat.
The main benefit to me was the easy reload of cord and none of those annoying break offs and having to undo head to refeed cord. Just simply need to have a supply of cords cut to length carried on you and only takes a very short while to reload.
Recently bought a replacement just to have on hand if the original ever fails.
I’ve had one of these for 7/8 years and they perform very well
Decided to upgrade to a new one in case the old has small cracks and depreciation.
Just being careful with something spinning at 10,000 rpm’s