My take on the term advisory is that it is not mandatory because I don't believe TCAS has a terrain warning included.
If RA says descend, you descend. If you hear GPWS Pull up, then up we go. In this case, the RA is not binding and thus is just advisory, whereas the GPWS is more pertinent..
Only other time I can think of ignoring this is in an emergency descent, possibly with an uncontrolled fire on board and perhaps in the circuit, if visual with all traffic and ATC are providing full coverage. Lastly, if the system is spurious, and only if this is confirmed, then i'll switch it off with a CB. Still not ignoring the RA however.
Failing this, I'M ALWAYS following RA.