As far as coatings or for that matter any parts, I am less interested in looks/appearance than I am the overall performance. EGT's and any small flow enhancements would be worth it for the pricing I have seen. Ceramic coating an exhaust housing looks to be approx. $55-75 plus shipping. So the "paints" are not what I am after,the ceramics have my interest as well as other specialty coatings for inside and outside of the housings.
I like to bump the performance minimally and try to maintain mileage, and as always preventitive measures to achieve minimal downtime, that is most important of all.