Migrating from Magneto 1 to Magento 2

I migrated all my settings, products etc from M1 to M2 recently.

Our old site has while developing our new M2 site gained new customers and products. So what would happen if I choose to migrate my data from M1 to M2 again?
As in this command: php bin/magento migrate:data –reset

Would the old products be overwritten and new products, customers be added or would it create duplicate products, customers and what not?

Thanks in advance.