I want to upgrade my newly acquired Centurion Ironman to STI and dual pivot brakes. My first inclination was to keep it all in the 105 family like the bike originally came with, and go with a 105/ 1056 groupset. But now I come across a very complete RX100 groupset, and I am wondering- is there any really difference between the 8 speed RX100 groupset and the contemporary 8 speed 105 groupset? If you look at the components:


They are the same except the 1056 has grey powder coating(?) . Same with the crankset- it looks exactly the same aside from the grey powder-coating. Does anyone know if the RX100 had inferior bearings or something subtle like that? How did Shimano justify the price difference?