Gillette pretty much ruled the roost when it came to double edge razors because they invented the double edged blade back in the early 1900s. They did get tons of competition from dozens of knockoff companies through the years, and almost none of those razors are junk, either. Literally hundreds to find today. But for me, Gillette mastered the double edge razor, especially up in the fifties and sixties when they invented the adjustable. That allows you to use different types of blades that are still available, but with different settings that makes for better shaves depending on the blade (stainless vs carbon steel; ultrasharp vs moderately sharp, etc).
I noticed that Gillette ran commercials to debunk certain razor styles....that they themselves promoted 2 decades ago. Like showing a razor head moving with the contour of the face. That is not what is needed or desired. The skin is soft and flexes, the razor should not.
They are slightly aggravating me by trying to sell to millennials.