Originally Posted by cazzooo
I understand one pulls from from top and one bottom, but what difference does it make? Can you use either one just as well?
The traditional bottom pull derailleurs which worked fine for road use had cable run vulnerabilities to dirt thrown up when used on mountain bikes. The mountain bike solution was to redesign the cable runs through less vulnerable locations above.
The top pull fders usually have a cage shaped for a 46-48T large ring so would not shift as well on a 52-53 large ring. Conversly, a bottom pull road bike fder would not shift optimally with a 46-48T big ring. With some bikes (not all) one would need some extra contortions to run the cables to the fder on the opposite side.