Fully appreciate that without the same kit to test e.g., pedals I can’t hope to conclude which of the two power meters are off or what the delta is between them. However I do know these were two very similar efforts - within a week - and that 17% difference is far too wide a gap to not assume that one of the two meter’s is way off the mark and given the numbers I get from my road bike I’d say the Wattbike is 10%+ over stating power.