I've generally used DuPont paints mostly because it is most easily available. I also used R-M on one project - nice - but that supplier didn't last the economy ripple before this current one. PPG is available, but much further to get to the suppliers and I don't care much for their primers, preferring SPI (Southern Polyurethanes)sanding epoxies and 2K. I don't care much for DuPont's Nason (sorry Robin) having used their clear on my '31 fenders and it has gotten a bit hazy while the rest of the car is SPI Universal clear. One paint that I've seen lately that I like are the DuPont Hot Hues - vivid is all I can say, plus deep color.

Any of the national brands are good along with a few of the smaller ones like SPI - it's the prep for paint and application along with the final buffing that makes them show car worthy.