Are you comparing just the frames or the complete bikes?
The reason I ask, is that I don't think the FSR 120 is available as a "frame only" without being an "S-Works".
If you are comparing the 120 Pro with the S-works then the difference is evident with the components.
If you go to Specialized's website and go to the Stumpjumper FSR section and their pull down menu links you to the S-Works frame.
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