Great question. In my former jurisdiction (45 inspectors), we had combos and individual experts. For commercial, we often sent 2 or 3 inspectors out for complex jobs. Often the inspector was combo-certified, but specialized in a particular area. In my current jurisdiction (4 inspectors), they are all combo. Basically, you can't afford to specialize when your staff is small. Same thing with plans examination - some large jurisdictions pass the plans around to 2 or 3 plans examiners, based on specialty. I agree that any combo inspector is going to be stronger in one particular area (based on his/her previous employment & experience), but cross-training makes everyone better and more versatile.