well I belive the fast is a more agressive ball. The fast is 0.038 diff while the Mars is 0.022 I belive.. Also take into cosideration the mars cover is weaker, even tho a solid/pearl hybrid. I have seen the fast in action, much more hook then expected for me, I personally had the street rod, i belive the core is to strong IMO, at least for my game.... With this being said I would slect the mars, its going to be much more predictable. Ask your driller.. he knows best

The cover on the Mars is more like the old Storm Curelyon that was on the original Hot Rod.  The Mars will get through drier heads much cleaner than a Fast.  The Fast is a stronger ball with more angle at the breakpoint.

I'd go with a Mars for drier lanes and a Fast for medium-dry when you want to generate angle.