POLL-Paint or undercoat?

I just went straight POR-15 when I did my floors and roof. Since it's all covered in carpet and headliner you never see it, so color didn't really matter to me. I have some extra foil back insulation under the carpets to try to help cut down some heat and noise on the cheap. Drove the car around when I bought it without carpet or headliner, amazing the difference in sound just putting those in.