I've found you get what you put into the covers. I had an "evolution" cover for my Saturn years ago. It was cushy enough that it offered some protection from things bumping into the car, falling tree limbs, etc; unfortunately it turned into a waterlogged mess after any amount of precipitation. It was also <span style="font-style: italic">very</span> bulky.
When I got my Miata I started using Weathershield covers. The lightweight version (Weathershield HP) looks like a nylon cover but water tends to roll off it and doesn't penetrate the fabric. It will leak slightly in the seams but not much. Weathershield HP is very lightweight, smooth, doesn't scratch paint, and can be rolled up to fit in a small plastic grocery bag for travel. The only downside is it can be difficult to control in high winds.
The weathershield HD is a heavier-duty cover that offers excellent rain and UV protection. The fabric is <span style="font-style: italic">much</span> heavier than the HP version and is a lot easier to use in winds - plus it doesn't tend to billow out as much as the HP in storms. Like the HP version, rain just rolls off the fabric.
I have a medium-weight indoor cover for my MGB when it's in the garage, and a Weathershield HP for when it's outside.
The medium and higher priced fabrics come custom fitted to your car from Covercraft. I've been very happy with the fitting on both the MGB and Miata. <span style="font-style: italic">All</span> the covers come without holes for antennas but they come with plastic grommet reinforcement kits for you to put the antenna hole in yourself.
My Miata has always had Weathershield HP or HD. The car is 9 years old, has always been parked outside in direct sunlight. I ripped my first HP cover pretty badly and replaced it with an HD, that one finally got eaten up by the sun and was replaced by another HP last year. The paint isn't perfect but it's a darn sight better than most cars parked outside in Florida for nearly 10 years
<span style="font-style: italic">Taken at work, the only time the car gets parked inside</span>
The bottom-end decent fabric covers should run $80-$100, aren't custom fitted, and aren't the best except for occasional use - but they're better than the $50 autoparts dust covers. A custom Evolution-fabric cover should run in the $155 range. The Weathershield HP around $245, and the HD another $50 more.
I and several friends have had good luck dealing with Car Cover World. They have a good description of the fabrics available
here, prices and options for custom covers are
here.
Awhile back I took some pictures of my weathershield cover in a thunderstorm. This water repellent nature will tend to diminish as the cover gets worn out, but this should give you an idea of how well it works. Except where there is some minor leakage around seams, the paint under the cover will be dry. Moisture generated by condensation evaporates through the fabric and seams quickly:
Click to enlarge...
Click to enlarge...
In general you get what you pay for (an HP cover lasts me about 4 years, so $60 a year for decent protection is reasonable to me - your mileage may vary).
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