Acrylic Enamel vs Acrylic Urethane

I've sprayed a solid color single stage one other time. It was on JohnnyDart's 65 vert engine bay. It seemed to go down pretty well and still looks pretty good. I dont recall what it was exactly.

The flake/poly in the mopar colors are not that big. Im looking for whatever lays down the best and I might be able to cut and buff. But then again its only the engine bay.

How soft are the enamels? Ill be installing the engine very shortly after painting.