These days with a good paint it boils down to what you are painting, from what I have learned. If you are painting a solid color, the PPG single stage is all you need. The painting process is simpler and the guy selling the paint tells me it will last as good as the basecoat/clearcoat and saves $. However, if you are spraying a pearl or metalic color then go with the basecoat/clearcoat approach to get the depth and some ability to make minor repairs later. This is just what I have been told over the years. My Jeep is going single-stage since it is solid Jamiacan Beige, but my Triumph went BC/CC since it was painted a Dodge Viper blue pearl.
Sincerely,
Mark