I think what you will find is that the reactor media that is he size of crushed coral dissolves better because it has more surface area for contact with the carbonic acid that forms in the reactor. This also means you need to be more careful with the controller setpoint...too low and it turns to mush.
The larger media can take a lower setting on the controller without sludging up.
I use the large size media because that is what GEO recommends, and I have GEO reactors on my reefs.