Howard, I had to do something in a timely manner if I was going to get the car built before November 1. I opted for the powdercoat because my car opens up the way it does -- and because I'm planning on putting it local shows.
Chassis Black, as Angela noted once, is a standard color and a durable option. I'd go with what the builder is set up to do, since they're able to do it before the body goes on.
Also, the chassis of my car was welded onto in so many places, cut and reformed, that I had to have it all sand-blasted clean. The spots where VW initially built and painted the metal 40 years ago were all, without exception, beautiful under the layer of protective grease and grime.