I have the old and C4 versions. Much prefer the C4 because of the tailcap design, 2-way clip and slightly better tint. It's claim to be brighter than its predecessor, but in actual use, it's hardly noticeable. Also, I've noticed that the C4's head and body have become a single part, unlike the previous version where I can unscrew the head and lego the body with a Fenix LD01 head for a 3-mode powerhouse. The limitation of Microstream is that it's one-mode and the output is about the medium mode of some 3-mode AAA lights. I don't really see that as a handicap if I want a light that's consistently switched on at a output I want without having to surf through multiple modes. Oh, love the forward clicky too. For $20, it's definitely worth getting.