Fluid borders provides better competition between jurisdictions. A community would have no reason to join a higher taxrate jurisdiction unless they were getting value out of it (e.g. better schools, trains, police, etc.). That's a good thing.

Though I fully acknowledge that I'm ignoring significant issues. e.g. what if NYC drops billions on a new trainline, and then some neighborhoods benefiting from the train line switch away from NYC. Are they still obligated to pay to maintain the train line?

Things like that.