In reply to various: Lots of sensible answers.
For me this issue boils down to there only ever being 3 reasons to use a screwgate (or back-to-back krabs) rather than just a normal wiregate/snapgate krab:
- it is a single point of failure.
- it is out of sight.
- it is in a high risk position susceptible to both being disturbed and not to be continuously loaded (e.g. clipped to my tie-in loop).
Once you have a clear set of criteria, I find it is easier to make objective rather than subjective decisions. It is also then much easier to explain your actions to other climbers.