I've been wondering for a while what determines "quality" in GP-software.

I've previously used the proprietary product Discipulus, but didn't like it
due to it's very closed nature.

I'm wondering if there are differences in how different software produce
their results, and if the difference will matter.
Could there be some solutions that either ECJ or Discipulus (or other
product) will find, while the other never will?

I've been using ecj for quite a while btw, and think it's great stuff.
Big thanks to Sean  (And everyone else involved) for all his efforts :-)