IMHO, power balance is pretty much worthless. It doesn't measure each leg independently. (it breaks each pedal revolution in half) In using it for 8 months, I haven't found any usefulness for the power balance data.
So I'd buy the Riken if your price concious, the Elsa if you're weight concious.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.