There actually was a scientific study last year as to the durability (lasting effect) of various car polishes and waxes. I realize that I am somewhat biased, but Zaino did come out on top. Meguiars was actually somewhere in the middle if I remember correctly.
Mike I must say though that I really like the Meguiars quick detail spray.

A funny side story that I just realized is Juans post number...469! Tell a woman "For a 69" call Juan! Everything with Juan has some sorta sexual inuendo.

 

It's funny, Juan and I registered in the same month (Feb '04), but I have a few more posts than he does. However, Juan didn't really start posting until he got his car about what, 2 months ago? And in that time he's managed to rack up 469 posts. Juan, that works out to about 8 a day man. You really need to get out more.

I've been a pretty consistent poster over the last 14 months, and I've averaged just under 3/day. Ok, I guess that's still pretty pathetic!

 

"It would take a serious independent study to say which one is better. I personally use Zaino because it's easy on/easy off, it lasts a hell of a long time, it makes my car look great, and according to their website, it's some pretty space age stuff that's good for my paint. (There's that marketing stuff again!)"

"Guru Reports"

Wax/Polish shootout.

Compared 46 different products using: Shine, reflectivity, duribility, protection, ease of use, availabilty (Zaino took a beating on that one), etc.
There were several Meguires products in this shootout.
Zaino WON despite the bad availability rating.