but it is a game of statistics in the first place.
Exactly.
If we were sure
everybody else has got a TCAS, it would be better to set TA only.
If we were sure
nobody else has got a TCAS, it would be better to leave TA/RA.
The important thing to remember is:
always follow the RA!
This has been covered in other threads, and one can download the Eurocontrol bulletins on this matter.
And in the extremely unlikely case in which you get a CLIMB RA during the descent, follow it!
LEM