I was looking into this recently myself. I'm in Eastern WA, and get plenty of sun, most days in the summer, but some of the land is deep woods, so I was also looking into lower light efficiency options. When I first got started, I read that mono cells were the most efficient, and MPPT charging helps handle some aspects of partial panel shading, so I've been kind of a snob about only buying mono panels. Then I found Will's youtube chanel, and seeing the results of his tests with poly panels, it kinda seems like it doesn't make a huge difference. I still think it's important to use an MPPT charge controller though.