Hi All what Rear Derailer is better My first choice is a Shimano XT RD M770 Rear Derailer 9Spd Deore XT rear derailleur delivers reliable and precise shifting with a stiff and lightweight open design Rapid Rise.All-alloy construction leads to lower weight without compromising strength and durability. Four fluorine-coated link pin bushings make this one of the slickest shifting derailleurs on the trails High rigidity wide outer link braces the pulley body to increase pivot joint rigidity Mega9 compatible for use with 9-speed drivetrains Durable sealed bearing tension pulley for low friction and smooth running of the drivetrain Low normal spring uses the spring to select lower gears, best suited to use with Dual Control levers Top normal spring uses the spring to select higher gears, best suited to use with Rapidfire shifters Rubber bumper reduces noise when used on non-conventional frame designs and my second choice Shimano XT 772 Rear Derailer 9Spd Shadow features a super low profile design that reduces the risk of damage from trail side hazards Single tension spring prevents contact with the chainstay resulting in a silent ride Direct cable routing prevents snagging from any trail side hazards All-alloy construction leads to lower weight without compromising strength and durability Four fluorine-coated link pin bushings make this one of the slickest shifting derailleurs on the trails High rigidity wide outer link braces the pulley body to increase pivot joint rigidity resulting in a crisp shift Strong return spring for a positive shifting feel SGS cage for use with triple chainsets Mega9, 8 & 7 speed compatible Durable sealed bearing tension pulley Top normal spring for use with Rapidfire shifters
