Can anyone tell me the difference between these two gruppos. I just bought a new bike that I believe is equipped w 7800 (according to spec sheet although how would I know?).

I found some good closeout pricing on replacement chains and casettes, but the casettes say 7800 and the chains say 7801. Will performance be better if they are exactly matched? Do I have to worry if my shifters are 7800?

I also heard that Ultegra 10 chains and casettes are more durable, i.e. will last longer w similar performance and therefore were a better 'value'. Is this true, or just hype from someone trying to sell them to me?

Lastly I assume I can also purchase 7900, but since it costs more I assume there isn't much benefit (i.e. some are a tad lighter, but again I assume they are optimized to work in a 7900 drive train, and I know the new 11-28 casette is not back compatable with the 7800 RD).