Are vinyl gutters practical in the South, where they will be subject to fluctuating temperature extremes for a few weeks in January and February?
I would worry about longevity with constant exposure to hot sun with vinyl. Temp extremes? Huh? Those are up north where it gets hot in summers and cold in winters. My experience in both WI and FL has been with the metal ones. Aluminum does not age while vinyl does. I have critter damage to some plastic drain options at ground level and flowerpots, suspect that would happen near roof as well (squirrels I am told). Metal can bend while vinyl cracks…
My vote is to go with metal in any climate.
I would go with aluminum. Vinyl is good for ground contact, but I would not put plastic up on the roof. Any plastic ages and becomes brittle when exposed to oxygen and light; some just do it slower than others.
Aluminum…and try for seamless.
Heavy duty aluminum if you are in an area that gets hail.