The 190/55 has quicker turn in and is approximately .3 inches taller. It corrects some of the factory speedo error and IMO feels more stable while leaned over in a turn. I am on my fourth 55 and don't see myself going back to a 190/50.
There are quite a few threads that debate the pros and cons of them (I don't personally think there are any cons).
^^^^^^^ what he said 100%. I was using these tires back when they first rolled out.
