BTT. The big improvement was by Cree, Inc, in 2010 - a high-efficiency LED that knocked everything else on the market out of the water. I have a half-dozen cheap flashlights with these and they’re better than anything I’ve ever used before. And did I mention cheap?
All of my original surefires, including my old 6Z, have CREE modules in them. www.dealextreme.com is a great place for emitters and modules.