Originally Posted by
Reddleman
For me, I chose Microshift Advent to install on 406 wheeled folding bikes for the range available on 11-42T and 11-46T cassettes for local hills, the wide choice of shifters available, the longer lifespan of a 9 speed setup over something with a skinnier chain and more sprockets, and the total cost (both for the original installation, allowing me to avoid buying another chainset, and the ongoing lower costs of 9 speed setups - 11 speed cassettes cost 3 times as much as 9 speed cassettes here, about as much a rear derailleur).
A 9s setup doesn't necessarily last longer than a 11s setup.
Its more the quality of the components than the number of speed that make the difference in durability.
And the difference of cost is also at least partly linked to the quality of the components (another part of the cost difference is linked to the difference in weight). 9s components are nowadays low end (because people looking for high end want also 11 or 12s, there is no market anymore for high end 9s) and for this reason often lower quality.
For the chain, Shimano (and SRAM) chains aren't very long lasting (even the most high end of Shimano), KMC and Campagnolo last longer.