I like trying things that are different. The Gran Sport is the first derailleur to popularize parallelogram RDs. I also have a modern Centaur group. I honestly don't see much difference between the two. The Sport has a single jockey wheel and shifts like crap, but still an interesting experience to get it right. I will figure out the OMAC and I am still searching for a frame for the Vittoria. I have tried a Vittoria once on a friend's bike. I did get to shift but it wasn't pretty. I'd like to also try a cambio corsa someday too.