If you want to remain "original" that meant Glasurit or Sikkens in the past. But PPG makes a fine product as well, and they've been a supplier to the Greer SC plant, at least, as well.
The more important factor is that the painter knows, and is skilled in the paint system they use, regardless of brand.
When Caliber Collision was buying out indie shops left and right, they were also making some changes in operations. One specialty shop I was familiar with was a long time Glasurit shop, and had to change. They lost one experienced guy, and his decades of institutional knowledge to retirement. Those who stayed had to adapt to the new system.
All three make quality product, and you won't go wrong. What you're shopping for is the quality of the job, which is harder as indie shops have become more scarce, and the pre-negotiated arrangements between the insurance industry and shops lead to more assembly-line/volume quality of work, not individual craft-level work. It's hard for indies to survive if they don't have the steady pipeline of insurance jobs or referral business.
That shop, which catered to and had a reputation with BMW owners, sold out after it lost the referral business from the local BMW dealers, business was hurt, and the owner decided to move on. The family member who was running the shop jumped ship, to the insurance side of the business.
