I have two Mars 4.0 blinkies and I find that they are junk in comparison to my one PB superflash. The reason is that both suffer from "Turn Itself Off Syndrome". Quite often I find that both of my mars 4.0s would shut themselves off by the time I got home from my ride. Even with brand new batteries. The issue is from the spring inside on the side of the light that is subject to the downward forces of bumps in the road. I managed to remedy this on one of my mars 4.0s by shoving a small piece of paper to remove the play that the spring provided, thus keeping the battery in constant contact with the upper terminal. If allowed to "bounce" too much, the battery would arc and corrode the terminal. Over time, the ability to turn on the 4.0 would diminish until the contacts were cleaned.

One of my Mars 4.0s had the clip break under normal use within the first 4 months of use. I was riding along the road and it just broke. It wasn't even an especially bumpy segment.

I have had zero issues with my PB Superflash. I do think the 4.0s are brighter, and I was really excited to have them at first. Now I will never buy them again.