Advantage:
Compare to PERM:
Perm application need be supported by company or institute. It is much easier if your company support you. NIW is hard, but you don't need be supported by institute. Another word, you are free. You can change your job, of course only in the similar field. But for PERM, you cannot change job. So if your NIW I-140 was approved, it is much better than PERM I-140 approved, especially if you cannot I-485 in the near future.
Compare to EB1: are you joking?