I appreciate they serve different purposes, but I had some unknown bottlenecks I wanted to discover, and explored 3 ways of doing so. In my case, one was far easier to actually gain any insights from than the others :) FWIW I use Xdebug regularly during development anyway.

Ah I see, my mistake, yes I wouldn't look to xDebug to track down performance issues admittedly, it's too cumbersome and limited as you've noted. My use case for it's profiling is simple comparisons between changes, to see if what I've done did infact improve a specific performance issue. New Relic is a godsend when you're trying to track down production performance issues, especially of the intermittent kind.