Here was my thought process (basically) when I was deciding on which type (mechanical vs. fixed) blade to use:
Mechanical blades need to use some of the energy they have to open the blades on contact--not very much, but some. Fixed blades, as I see it, should have energy stored to maintain the penetration...
Yeah, so I guess maybe its some screwed up physics in there--but that is (in a nutshell) what I thought when I bought my broadheads...maybe I'm wrong--but I wont admit it
Either way, a lot of personal preference with the broadhead type--just like most other aspects of bow hunting!!!