Originally Posted by alfeng
If you think you may want to use a 50/34 or 50/36 chainring combination with a MTB Cassette, then a long cage would probably be a safer choice.
If you will be using a "compact" crankset with a regular Cassette, then a medium cage would be fine ... of course, a short cage is fine if you will be running a tight Cassette.
So, IMO, your derailleur choice can be as much a cosmetic choice as anything ... with availability the limitation for an XTR 950 rear derailleur vs. your wallet being the limitation for a recent/current medium-or-long cage Campagnolo Road rear derailleur.
BTW. Campagnolo rear derailleurs are comparatively porky when compared to a presumably equivalent-grade Shimano rear derailleur.
To put in some numbers… the new 10 & 11 spd SRAM & Shimano standard rear derailleurs work fine with a compact (50/34) or standard 53/39) cranks and 11x28 cassette.
Regarding Campy 10sp groups, I've been riding this on a road bike and on a CX bike since it first came out (yes very first generation of 10sp) and a few observations:
- Campy by far has THE BEST front shifting. Yes I also ride and work on Shimano Dura Ace and SRAM Red. IMO in terms of shifting performance and ease of setup the D/A is a close 2nd to Campy, and SRAM Red 10sp front shifting sucks. Several friends have replaced their Red and Force front derailleurs with Ultegra 10sp front derailleurs. When setup properly an Ultegra FD will shift just fine with the SRAM paddle shifters.
- When working properly Campy 10sp rear shifting is great. So are SRAM and DA. Different feel so with DA being the lightest and Campy being the "heaviest" click (clunk?). I have better luck setting up and tuning in Shimano rear derailleurs. I can get Campy and SRAM dialed in, but for me the Shimano seems to be easier to adjust. At the end of the day all work great.
- Campy rear shifters wear out quickly. Fortunately they can be rebuilt. Unfortunately the part that breaks is about $30. More unfortunately it's about $75 to have the LBS pull the rear shifter off the bike and rebuild. The owner is a great mechanic so I don't mind so much, but I figure a rebuild every 5k miles or so. This is consistent with my 10sp Record & Centaur shifters and my wife's Chorus 10sp. FWIW the Campy front brifters have NEVER needed any work. It's nice to be able to rebuild shifters, but IMO the 10sp Campy rear brifters wear out too quickly.
- Campy bottom brackets have been a mixed bag. The Record internal BB on my road bike died after 2k miles or so. Waaaaay to early IMO. The CX had the Centaur BB and that lasted longer which is great considering I pampered the road bike and the CX lived on gravel roads and mild single track. Replaced the Centaur BB on the CX with a Chorus (much lighter) and have been even happier with the Chorus as it's been working for more than 10 years now. Replaced the standard Record crankset with a Chorus compact with the external bearing bottom bracket. This has worked great!
- When I went to compact cranks on my road bike I did not replace the FD - I kept the standard Record FD. Did I mention Campy has excellent front shifting? Never miss a shift. Never drop the chain. Ever. Period.
- Brakes are excellent with Shimano and Campy. My bike with SRAM Red has Specialized house brand brakes that stop fine but the quick release barely spreads the brake shoes so it's a PITA to use 25mm tires. Keep thinking of getting a cheap set of Force brake calipers which will work better, but I've been too cheap.
- Cassettes. Last item… If I keep an eye for sale items can get a very nice Ultegra 10sp Shimano cassette for $35. The better Centaur 10sp cassettes are $100 and up. Last I saw, Record 10sp cassettes were in the $300 range. Not only that, but Campy simply doesn't make the gear ratios I want/need. My fav is the 11x26 and 11x28 available with Shimano and SRAM. The Campy 11x25 is good but for long days in the mountains I'd prefer a bail out gear. No I'm not a mountain goat…
I'm in the process of planning the build for my next road project and will be opting for Ultegra 11sp. Price and gear ratios are what drove me from Campy. For me the 11sp 11x28 cassette is sufficiently tight for racing a pancake flat crit and still gets me a bailout climbing gear. This will be my first 11sp bike.