By far the best material for clearity, UV light stability and scratch resistance is acrylic, sometimes better known by the trade names of Plexiglass, Oroglass or Perspex.
It can be heated in an oven until it becomes rubbery (about 180 deg C if I remember cporrectly), then it can be laid onto a simple mould (a pice of curved wood for example) and formed over it.
It has 2 potential problems, one it is reasonably brittle, and two, it is quite flamable.
It was developed during WW11, where it was used to replace glass in aircraft canopies and windows. It is still used for this today.
It is also very popular even today as automotive wethershielsd, headlight and bonnet guards, badges and tail light lenses, and windows in race cars.
It is also used extensivly in the sign industry.
Polycarbonate, while much tougher, is poor to scratch resistance, and moderate to UV, although it can be modified to improve both. It is also quite difficult to mould, as it absorbs moisture from the air, and if heated to moulding temperatures, before drying, it generally blisters or bubbles, and loses most of it's impact strength.
Unless you specifically need the extra impact strength, or higher temperature resistance of polycarbonate, acrylic is by far the easiest way to go, and generally has by far the best ballance of properties, unless you use very specialised, expensive, modified grades of polycarbonate.
Standard polycarbonate, also has very poor resistance to some very common automotive fluids, ie the aromatic hydrocarbons found in virtually all modern fuels.