car covers ? which one is the best?

If your looking for a Car Cover that Totally Protects your Stang from the Weather then there's None out there. The GOOD Car Covers are Water Resistant, but they will let the Rain and Snow through them, they have to Breath.
I park My Mustang on the Garage through the Winter and I bought one, a top quality one for over $100, and it says it's only as good as it can be, rain, snow and the rest will get through it, Im pretty sure mine was made by Dupont.
You have to look at it this way, a Car Cover cant resist everything or it would be like putting a piece of Plastic over your Stang and that would make it SWEAT and cause more damage than just leaving it uncovered, Mold, Mildew, ect....
Car Covers are only good enough for Protection from Dust, Debris, Tree Sap, Bird Droppings ect....
If your looking for one to Protect it from Rain, Hail, Snow and think when you take it off it's gonna be as you left it than your on for a Big Surprise. What are you looking to Protect your Stang from??? If your just looking for one to keep your Baby dust free and Debris free than get one that (Brethes) that's about all you can do, you need it to breath to let out Moisture, it's almost like a (Gortex) cover like in Hunting Clothing.
A decent Car Cover will cost about $50, the Best Car Cover is a Garage and will do the Best Job:bigthumbsup

This is the one I have. New 2005-09 Ford Mustang Custom Fit NOAH Car Cover | eBay

It's made for wet areas and it doesn't get much wetter than northern California in the winter time. It has a 4 year guarantee
and is sold by the California Car Cover company.

Two years ago I bought an inexpensive ($90.00) car cover and it only lasted a year. You get what you pay for.

I have a blue CoverCraft "Evolution" cover that I bought in 2006. It has been on a car, either in the garage or outdoors (80% of the time), as long as I have had it. It still keeps the sap and stuff off, and all but the finest dust. Early in its life it kept the dew off, but not the rain. Only trouble is, as it aged it lost some of the fuzzy inside material, and something in one of the layers turned to white dust. On the white car, no problem; on the black car, you have to California-Duster it before driving.

I had a tan Evolution cover of the same description, no deterioration in the two years it was used (20% outdoors, 80% indoors), but someone stole it a couple of months ago.

I now have a gray "Noah" cover with the cable and lock, and it hasn't been stolen after about a month in the driveway. It had the license number painted on it; maybe this new paint job will be more of a deterrent.

In 2006 I paid almost $200 including S&H for the blue cover; in 2009 the tan cover cost about $220; the new Noah gray cover cost $265 shipped, including the storage bag and cable/lock. There are better deals, but the CoverCraft items are a good compromise whatever the price.

Getting the cover to fit in the bag is not a simple matter; I wouldn't have bought it separate, but they sent me that instead of the cable/lock I ordered, so I let them send the latter without returning the former.