Originally Posted by
himespau
Top tier is actually less durable (though gets new technology first that later trickles down) because it's made to be light above all else. 2nd or 3rd tier is probably the sweet spot. Especially if you're not racing. The tech has had time to mature as it trickled down and the components are slightly heavier duty.
Several
RD-M952 XTR rear derailers I have would disagree. The one on my commuter has about 25,000 miles on it and the one on my touring bike has about 10,000 miles on it. The 9 speed XO drivetrain parts (shifters, front derailer, and rear derailer) on my mountain bikes would also disagree. High end parts aren’t delicate. They do weigh less but that hasn’t had much of an impact on their durability.
On the other hand, modern (post about 2010)lower tier parts started getting a whole lot better. Alivio from 1999 is heavy junk. Alivio from today is actually pretty nice. It’s lighter
and more durable.
There is also a dirty secret on road and mountain components from Shimano. They make great rear derailers. Their top shelf stuff is excellent. They make crappy front derailers. Or I should say they make crappy expensive front derailers. They just try too hard. Their road fronts are finicky and limited in range. Their mountain fronts have had many missteps. From the independently operating plates on the XTR to the carbon E-type front, they have made misstep after misstep. Tiagra and below on the road side and Deore and below on the mountain side are cheap, easy to set up, and durable. Anything above those levels is just too difficult to deal with.