I've used Llumar Diamond, Vkool Elite and 3M Crystalline.

IMHO,

No. 1 is Llumar Diamond,
No. 2 is 3M Crystalline, and
No. 3 is Vkool Elite!

Why?

I've used Llumar on long distance and to my surprise, it really gives the occupant protection from the heat! I enjoyed my way without blasting my AC.

3M is good but somehow, my smartag cannot go through. I believe it really depends on the car's windscreen. Some can whereas some can't.

Vkool Elite, heat protection is good BUT... after 2 1/2 year, the film started to peel... So, I had to claim it under warranty. After that, am not too sure coz I sold off the car! To me, this means quality is a question mark!

Cheers!