- easier maintainance, since you can clean panels with a roomba-like rover instead of walking down with a hose. Replacements don't require ladders and cranes, since panels can be smaller without requiring more support
-more heat may be irrelevant and anyway it's speculative
-no plants growing under them to constantly be trimming
- harder maintenance
- more heat, less efficiency
- will accumulate dirt and other debris with no tilt
- will be damaged by animals and platnts
- bigger ecological footprint (not everything is carbon; we share this planet)
- better not be in any sort of flood plain (unless you think it'll survive the removal of an inch of silt across its whole surface)