Why are cab units preferred for passenger service?

[steinjr]

I'm just curious: why are cab units preferred for passenger service when it comes to diesels? Is it just because of the appearance fits nicely in a passenger train? Aerodynamics?

Aerodynamics and looks. And not that much need for good visibility towards the rear - passenger trains rarely do much switching along the way.

Why not a hood unit?

Hood units are also used. The most important thing about a passenger train is that the train runs. Passengers get grumpy when the train doesn't run.

If the available engine is a hood unit, then you use a hood unit to pull your passenger cars.

Smile,
Stein