From a material standpoint, the 2 better outdoor materials are Evolution 4 and NOAH. Both are made by Kimberly Clark. They also make a super one for use in extreme sun areas, but I doubt that's what you're looking for.
NOAH is 3 layers thick, and Ev4 is 4. You get better door ding protection with Ev4, but it is bulkier. I prefer the Ev4 for its door ding and hail protection abilities.
Generally speaking, you want a custom fit with mirror pockets, and the cable/lock kit so no one steals the cover. Better brands include Covercraft, Wolf, California Car Cover, and Coverking. I'm sure there are more.
I own indoor and outdoor covers for all my cars, and wouldn't dream of leaving a car at the airport or in a store parking lot without the cover on.