What exactly is the difference between the Shimano high end (HG 93)
and the low end (HG 53) 9 speed chains? I know that the HG 93 is
labeled "for Ultegra/XT" and the HG 53 is labeled "for Deore & Tiagra"
but what is the actual difference.

Here the 93 is substantially more expensive then the 53 but if this
difference in price provides increased service then it may be worth
it.

I know that anything labeled "Ultegra" is, of course, better. But
better how? Higher speeds? Longer life? Better bragging rights?

Does anyone have any actual data?

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Cheers,

John B.