Standox, Spies Hecker, Glasurit, Sikkens have always been high quality. In general, european base has always been better than base from "the big three", IMO. PPG is overpriced and doesn't cover that great, and their lower lines are worse. Dupont never covered well, either, especially certain colors. Sherwin base (Ultra 7000) sprays easily and covers well, but will bite you if you don't let it dry completely before clear, you can't sand it, uses a special reducer and has gotten as expensive as DBC. That being said, there are good and bad qualities in all refinish products, but most can work if everything is done to the letter. I've sprayed at least 20 different basecoats in the last 30+ years, and none are far and away better than rest, IMO, but the top of the line bases from any company are what they base their reputation on, and are usually worth the money in the long run.