POLL-Paint or undercoat?

Since I'm re-doing the interior of my Duster, I am torn between doing paint or spray on undercoating after I remove all the rust and paint with rust converter.
Paint really, really looks good, but I am more concerned with performance than looks, as once the carpet is down, you can't see it anyway. Would there be any advantages/disadvantages for either, other than the obvious ones:
1) Tar (Undercoating) is very slow to dry and remains tacky for years sometimes
2) Carpeting and insulation might tend to stick to tar
3) Tar would probably do a better job of sound-deadening and sealing out fumes?
4) Tar does not look original (not that it matters)
On the other hand-
1) Paint is expensive
2) Paint looks 'factory' and is original
3) Paint dries quickly
4) Insulation and carpeting will not stick to cured paint

Anything obvious I'm missing? What are your experiences, pro's and con's?
Feel free to post any pictures and voice your experiences and opinions, both positive and negative!