The long cage will give you more chain wrap capacity, allowing you to run a wider range of gears. But if you're not going to do that, and you don't like the look of the longer cage, make the dealer send you the right part. Functionally the long cage will work just fine.
Originally Posted by
BikingGrad80
I recently had an issue with a long cage RD that the chain would rattle on the pulleys on the big CR and biggest 3 cogs. I replaced it with a short-cage and no more problem.
This has nothing to do with short cage vs long cage. It's an issue of not having the b-tension screw tight enough on your long cage RD or trying to run a cassette that exceeded the largest cog spec of the RD.
Originally Posted by
RoadGuy
Depending on how long your chain is (was it sized for the short cage derailleur?), a longer chain may be required.
False. Cage length has no influence on chain length. Chain length is set by the big/big combination.