I think your biggest argument in favor is cost and looks, it's much nicer looking than EC, which is tacky. Growth, both are fairly inert, geological mineral analysis is different than say nutrient or fertility/availability.
You should have had a plain rinse sand control and then a ADa AS or a mud, clay loam with a tiny bit of some osmocoat.
This would give you an upper and lower range comparison.
Also, you would be best off growing the plant emergent, this would remove any CO2 dependency between treatments. As long as the light was the same, then it'd be all up to the sediment type.
I'm sold, but for the above 2 reasons, looks much nicer/cheap.