In NY, you can take the NERB if you want to practice outside of NY, but to practice in NY you MUST do a GPR or equivalent residency (including specialty programs). Everyone takes the NBDE part I and II, and part I is currently what most residency programs use as admission criteria. Eventually, I believe there will be a specialty exam since the NBDE will go pass/fail in 2012, but more details on that have yet to materialize.