What the Desert Actually Does to Vinyl
Vinyl does not rot, does not rust and holds no interest for termites, so the things that end a wood fence never touch it. Around here it gets tested by something else entirely, and that is sun and heat.
The difference between the two ends of the vinyl market is exactly that, and it does not show on a sample board. It shows up in July, in the second or third summer, on the run that faces west.
Why the grade is the whole story
Good vinyl carries its sun protection blended right through the material rather than laid over the surface, and there is more material in the rails and the posts to begin with. That is what keeps a rail straight across a span when the surface temperature climbs past anything you would want to put a hand on.
A cheaper grade is thinner and has less of that protection in it. It stiffens instead of staying slightly flexible, so a panel cracks where it used to give. The surface chalks and comes off on your fingers. Rails begin to bow in the middle of a span, gates stop meeting their latches, and the white goes flat and a little yellow.
Once vinyl has gone brittle there is no bringing it back. You cannot sand it and recoat it the way you can with wood. Almost everything that decides how the fence looks in five years gets decided on the day the product is chosen, which is why the grade deserves more of your attention than the picket shape does.
The low-maintenance argument, honestly
Vinyl asks less of you than anything else you can put on a property line except block. No sanding, no staining, no repainting, and no season where it starts to look tired.
What it does ask for is a rinse. Dust settles on a white fence out here and a hose takes it straight back off. That is the entire maintenance schedule for a good vinyl fence.
Against wood the trade is worth saying out loud. Wood costs less on the day it goes in and keeps asking for attention afterward. Vinyl costs more on the day and then leaves you alone. The wood fence installation page covers the other side of that choice.