We haven't been good about compiling everything into a simple-to-digest format, but the thread,
DFRPG vs DF 1-19, covers what you're looking for.
For myself, DFRPG is the public face of my games because it's compact and beautiful. It draws people in. Behind the scenes, I supplement with details from the DF line or other elements of the broader GURPS ecosystem. I probably hit DF3 the most with its additional races and "multiclass" lenses.