Well, Sabu plays a heel doesn't he? He doesn't pose for the crowd, he shrugs it off when the people in the crowd reach out to him when he passes. Of course, he booked as a face, so he is a face. The one thing that distinguishes these two guys from everyone else in the WWE is the one thing they have in common. They're always booked as legit badasses -- heel or face.
Incedently, how will the crowd booing Sabu hurt him? You can't tell me they (and you) don't mark out when he busts out an Arabian Face Crusher.
Sabu is more a face that doesn't pander to the fans. As some places call them Face with an Edge.