Let's say that 5 people vote to close a question, all marking it "off topic". 4 people mark it to go to one site (e.g. server fault) and the fifth person marks it to go to a different site (e.g. super user). What happens in this case? Will the question just be closed, or will it be migrated?
It'll be migrated to Server Fault. The rule for migrations on SO is that 4 people must vote to migrate to the same target site, else the question will not be migrated. On other sites, the required number of people agreeing is 3.