Originally Posted by willtsmith_nwi
The stronger spring on a SRAM keeps the chain from tapping cadence on your chainstays. It also helps keep the chain on the rings where it belongs and reduces the incidence of chainsuck. The 1:1 (ish) actuation ratio makes the system more resilient to crud.
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On Shimano at least, the spring that controls the pull on the shifter cable is not the spring that controls chain tension.
I can see how increased chain tension might help keep the chain on the rings, but that has nothing to do with chain-suck as I understand the term. Chain-suck is when the chain is stuck on the middle ring because of too much force on the pedals. When the force is reduced, it flies off the ring and overshoots the small ring. It's a technique error and not related to chain tension.
Al