I have had the Blackburn Mars 4.0 for a year now and really like the light. I had the Mars 3.0 before that for many years and really like the amber side lights that give you some side visibility. I think that side visibility is an area most light makers ignore.
It mounts on seatposts without tools. 
It has a clip that will fit on any piece of webbing, jersey pocket, seat bag, etc… and it has a nice rubber gasket to keep the moisture out. That is something the Planet Bike Superflash does not have. Speaking of which it has a nice bright 1 watt LED like the superflash.
Blackburn says:
– Blackburn’s most powerful rear flasher
– 1 Watt Ultra Bright Red LED
– 2 Amber Side LED’s
– 50 hour runtime steady; 150 hour runtime flash
– No tool battery installation
– Two AAA batteries included
– Versatile mounting system with rack adaptor
LED’s: 1w Ultra Bright Red, 2 amber side
Run Time (Steady Flash): 50-150 hours
Batteries: 2 AAA