Almot, I have heard the same, that poly delivers more off peak light levels. Anecdotally, not side by side testing. I would love to see a test validating that. I have searched and not found one.
Anyone got data or a link?
Edited to add more: using my own case, space is a constraint.
One option was 4 x 140w Kyocera poly. Yields 560w and using 6,213 square inches of roof.
I chose 2 x 315w LG Mono. Yields 630w and using 5,084 square inches.
I could not convince myself the poly would ever make up the deficit in capacity. According to LG's published data the panel will make 20 percent of the amps at 200w/ meter squared, so output is linear down to at least that level. Unless the poly panels have a huge increase in low light level efficiency they cannot make up the difference.