GFO from Bulk Reef Supply is really the way to go. I have never noticed a difference between any of the different manufacturers of the media (rowa, phosban, BRS, etc). I tend to think that these guys are all getting it from the same source and just packaging/pricing it differently. If people are telling you they think one is better than the other, I would honestly like to know how they came to that conclusion, as it is pretty hard to test accurately for phosphates in the first place, and with all the other variables in your tank, it would be a PITA to isolate the effects of the GFO.
Anyway, to answer your question, Bulk Reef Supply has info on their site as to which version of their media to use (granules vs. pellets). If I recall correctly, one will produce less dust and is better suited to being run in a reactor.