As far as I've read the O ring is based upon an old design. The X ring is a newer design and is considered to last longer. It is all about whether grit etc can get in the seals and wear them down.
Anyway, here is a link to a page that descibed it all in one go:
http://www.quality-cycle.com/truth_a...cle_chains.htm
For me - I always hear about there being a differential between what an engine can output and what is actually gets transferred to the back wheel (Manufacturers quoted performance versus dyno tests). The only thing in between the engine and the wheel is the sprockets and chain. Therefore having a good quality set up must go a long way to reducing this differential.
But for me, foremost it is about making the chain and sprocket look a bit more in line with the rest of the bike. Any improvements is performance is a secondary bonus only.
Cheers
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