As far as I understand
-valve extensions are add-on tubings or hoses that have independent valve on the end and keep the original valve open all the time. .
-extended valve is a sleeve with pin inside, that is pushing original valve, while not holding the pressure in it.
The 1st adds additional connection to the set up, what proved to be weak link.
I personally lost a tire when I used tire equalizer without TPMS.
The 2nd seem to be pretty reliable, but still additional gizmo.
I think we have the same issue with new duallies, where none of 2 chuck designs would fit directly, but since the tires need air less than once a year, I just use flat chuck that goes between the tires.
Some additional work, but once a year I can handle that.
