Most often I don't get a choice. There is one system that makes sense for this because it is already in use.

My house was made in a standard system - the studs are 16 inches on center. The pipes are half inch (there is nothing half inch about pipes if you measure them). Using metric would be a big pain because the house was designed around standard measurements and so things are much easier to stick with it.

Our roads are standard. I can set my speedometer to metric - but then I'm in danger of breaking the law if I forget to convert. I tell someone "go X km and turn right" - but they won't know what a km is, and their odometer won't tell them either.

I work with farmers in Candada who measure crop yields in kg/acre because their local elevator buys their crop by the kg, and their land was measured in acres long before the country went metric - this is mostly about where they put the roads so land makes more sense when you measure in standard even though everything else in the country is metric.

I use metric where there is no reason in the real world to do otherwise. Which means I mostly don't use metric because almost everything I do deals with the world around me.