Len Stuart runs an autobody and paint website that has lots of discussions on various types and brands of paints. Before I painted my 67 230SL in DB White several years ago, I spent lots of time going through these discussions before settling on a paint system. Most of the modern catalyzed paints are very similar in color hold out and durability. All the shops have their particular favorites based on cost, ease of application, product support and availability. Len is a proponent of Glasurit but acknowledges that other companies like PPG, R&M, Sherwin Williams, DuPont, etc all have their proponents as well. In the end, I went with single stage PPG polyurethane and PPG undercoat products such as epoxy primer and primer surfacer and have been happy with the results. A big part of my decision was based on the discussions I read through on Len's website as well as the availability and support in the area in which I was living when I did the job. Hope this helps.
George