With a MSD ign the blue one on the left is most accurate and bright. The Flaming River is a very good light and simple to use on MSD systems. Reg ign systems I have had good luck with Craftsman lights. I had timing tape on one of my cars but it came off while ago so I picked this dial back Craftsman which works well on my Mopars with reg ign.

For a reg light, the Flaming River unit is hard to beat. IMO