[Heel n Toe]

I think the question you are really asking is "would either of these look cool on an Avalanche?"

Seriously though... any way you can keep the interior temps lower so a vehicle isn't so hot when you get in is a very good thing in my book. I just use one of those windshield accordion thingies and that's enough for me. Keeps the sun off the steering wheel. A/C cools everything off pretty quick after I get rolling.

And yes, it is a good idea to roll the windows down for a block or so to let out some of the superheated air.

I forget where I heard that (recently), but had heard that it wasn't a good idea for years.