If you carry more than 19 discs total. The Prodiscus will fit the bill. On the other hand, I would try to reduce my disc count to under 19 and get the Grip, before I'd get the Prodiscus.
I have both and the design on both are well thought out, but the material used in the Prodiscus are not top quality. I've already had a zipper break on the Prodiscus (easy fix though). I would say a good rule when buying a bag. Is that it should be made with Cordura and have thick gauge zippers.
If you do carry more than 19 discs and don't want to reduce that #. You might want to check out the Golf Mahal.
I played my final round with the Prodiscus bag today and I realized why I dig my Mahal. For ME, I love the fact all my discs are easy to get to. No flap or opening to small to were I have to contort my discs to get them out and it has a bit more storage than the Grip. Finally, the materials used it this bag are GREAT!
So I would say get the Grip over the Prodiscus, but look into the Mahal if you carry 19+ discs. Don't waist your money on the Prodiscus, because I don't see this bag lasting longer than a few years.