I usually go with the highest level shifter you can afford. The derailleur will simply be fancier metal or carbon cage. The shifters often go from using bushings to bearings, which can improve smoothness of shifting.
Also, bike yoke makes shifty (pulley for the rear derailleur that replaces the plastic wheel and bushing the cable routes around with a metal pulley and bearings). That can make a big difference
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Also, bike yoke makes shifty (pulley for the rear derailleur that replaces the plastic wheel and bushing the cable routes around with a metal pulley and bearings). That can make a big difference
Sent from my iPhone using Tapatalk