For the average consumer is there any advantage to installing a Mono versus a Poly module system?
I would prefer the most efficient module and hopefully one that I could trust. That being said, usually mono is most efficient, but if you were to look at a 260W polycrystalline module made in 2017 vs. a 250W monocrystalline module made way back in early 2016, and the brand was the same, I would go with the poly. I think there are some out there who would disagree with me and 250 vs. 260 is close. Maybe the 250 mono looks better or maybe it will work better in 2067 when I am 100.
If you are going to buy 20% efficient crystalline PV, it will be mono, because mass produced poly does not get that good.... for now.
If you want a good argument for getting polycrystalline PV, it takes less energy to make polycrystalline solar cells, so it is better for those that care about burning too much coal to make PV, although you can make PV with PV energy.