barit1,
I have flown some 737-500's with
VSCF's fitted. Identical in operation as far as the pilot is concerned, so identical that I think some aircraft even had a VSCF on one side and a CSD on the other.
We did have a UKCAA restriction on aircraft with VSCF's fitted that we had to stay within 45mins of a suitable airport rather than 1hr with CSD a/c, so maybe they were less reliable?
S&L