A well-run Pre-Check line such as at IAD/DCA, processed 6-7 pax for every one moving through the standard line. That is a combination of experienced Officers, a good physical setup and likely a more experienced traveling cohort.
It has to be a really, really long regular line to make me opt for anything other than Pre-Check.
Part of it is also that I am completely set up for Pre-Check. I simply dump my pockets into a side pouch of my briefcase (I don't worry about what is metal and what is not) and then add my phone once I've scanned my BP. Not worrying about shoes, coats, laptops and belts is worth something.
If you are with a non-pre-checker, I just wait for them or tell them that I'll meet them at a pre-determined spot.