Multiple UIDs or multiple master keys?

[Philihp Busby]

1: When revoking a UID from my key, it asks for a reason. What happened to reasons 1, 2, and 3?

Please select the reason for the revocation:
  0 = No reason specified
  4 = User ID is no longer valid
  Q = Cancel

2: What benefits benefits are there to having separate master keys for personal and professional use? Outside of not wanting the identities linked, because I am not yet famous enough for that.