Tech changes so my observations of my older panels may be outdated. That said my 230w poly kicks my 220w mono's butt in bright light and dim.
I pull 15a off of the poly and 12a off of the mono in bright light.
Drop the light levels and the mono's voltage drops fast, too the point it's useless. The poly produces at first light before the sun comes up, in clouds so thick you don't know where the sun is and even pointed away from the sun.
Living in "Sunny Colorado" you would think mono would be better. Last year most days were morning sun and afternoon clouds. The poly did well in the clouds, the mono would of had me on the generator.
