Quote - If there's no good reason over using one or the other...

I use PNU  (Poser Native Units). I spend a lot of time editing Poser library files (cr2, pz2, hr2, etc). As PNU is used internally in the library files, I don't need to do any conversions to get from the value expressed in the code to the value expressed on a dial, or vice versa. I would never dream of using anything other than PNU as my default measuring unit, though I might swap to some other unit if I ware following plans for the construction of some item, where the plans used a particular unit.

For people who don't often edit Poser files, then it is not very important which units are used, and comes down to a matter of personal preference.

Quote - ... should we consider informally standardizing on a metric and assume someone is using that specific length unless otherwise stated?

Yes, the application we are using is Poser, Poser uses PNU internally, all other units are approximate conversions from PNU, so we should assume PNU unless some other unit is specified.