An American who moves abroad maintains the status he had when he lived in the homeland. So a New Yorker who moves to Canada still can vote for his congressman, senator and the nation's president. (Quite exceptionally, the former New Yorker is also responsible to continue filing his state and federal tax returns but that's a separate issue)
Puerto Rican residents are usually US citizens but do not have the right to vote for representation in Washington, including not being able to vote for president.
So the question arises, what happens when a Puerto Rican moves abroad? Does he acquire the right to vote? Can it be that the former New Yorker and former Puerto Rican find themselves as neighbors in Vancouver, but one is eligible to vote for US president and one isn't?