by grarrrg
0. Mostly what he said.1. Almost purely cosmetic. 1 rule change, 1 card change, and some cards have updated wording (but are functionally identical).
If you have neither, get the new one. If you have the old one, you're probably fine as-is.
2. Clarification: the NY Power Up is essentially 2 expansions. One half is for NY monsters to use in NY, the other half is for NY monsters to use in Tokyo. You can't use both halves at the same time (without some house ruling anyway).
3. Children are small, loud people that like to make messes.