caute. mate niekto skusenosti s Di2? zaujima ma rozdiel medzi Ultegra Di2 6870 a R8070.
podla toho co som sa docital je to viac-menej jedno.

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although mechanical derailleur's difference are big, on the Di2 side is not so much.

Biggest difference is actually in the new Bar End Junction box (neater looking),
new Battery (that support newest Dfly) and new Dfly unit (EW-WU111). Get those version instead of the old ones.

FD lose weight and having a new cable entrance location.
RD Radically change appearance, having more chain tension, better crash durability but perform shifting pretty much the same.
Shifters, The old 6870 have two buttons per side. New 8070 gain third button on top of the shifter. Just like what 9070, 9150 and 9170 already had.