Curious- base coat vs acrylic urehane for base

Single stage paint is fine for a solid or, non metallic color. You can cut and buff it and looks real good. If your shooting a metallic paint then it needs to be base coat/ clear coat. You can't wet sand a single stage metallic, it messes up the flake.
I also keep in mind if it's going to sit outside all the time. If it's going to be outside then it should have a clear on it to protect the paint. A single stage paint will fade pretty quickly if its outside all the time, clearcoat cuts the fading out. I always tell my kids to take care of the paint on their cars...paint protects your car from rusting so protect your paint...