I am building a bicycle with Ultegra double on the front with XT on the rear. The cassete will be
XT 11-34. In shopping for the right XT derailleur I found 3 different ones.
Mid-cage(M-760 GS 9-speed), Long Cage (M-760 SGS 9-speed), and Top Normal (M-751 SGS).
Which one should I use?
What are the differences?