> /var for variable data. This is where you would put things like your Postgres data files.

This one never sat well with me. I think of /var as temporary data, something I can lose without much consequence. But never data files. I know it's the default, but still.

/srv I like because it seems like a proper place to separate server-related data, i.e. /srv/wwwroot or similar. But if you like /var, that of course would be the place for this type of data.