Seems overall the best way to import contacts with more then one address is to create a spreadsheet with columns in order of preferred primary address.
So now this set of data would create primary address as home for these imports.
Then next import would be of those contacts that need the primary address to be work
What if you already imported all the contacts but now have a set of contacts you want to switch primary address from home to work?
You could reimport all the contacts you want with the update feature.
So say for example a bunch of people have home as their primary but you want to make it work = primary then you would have to export all those contacts (both addresses) then swap the columns to the order of primary = first column group. For example you just exported a bunch of contacts and want to make sure the primary address is work your import would look like this.
This would tell CiviCRM to swap primary between work and home.