Plastic is the way to go if you have low water pressure. Another great feature of plastic impact sprinklers is they typically have the most even water distribution (close to the sprinkler head, to the farthest spray and everything in between). These also last many years. I have some mounted on the old garden area all year round for 5 years straight and they are still trooping along. Plastic is also going to be the least expensive option as opposed to brass.
That being said, Brass is going to be longer lasting, especially if left out in the sun. However because brass weighs more than plastic they are going to be less efficient with lower water pressure...and they also are typically not as good with even water distribution (though they can be pretty good, depending on the particular model/design).
One you should definitely steer clear of is the Zinc body sprinklers. They arent even a compromise between the other 2. They are typically less precise, less even water distribution and cheaply made.
These old Orbit Sprinklers are Made in USA.
