Recently had the chance to compare 3 different tints - V-Kool Elite, Llumar security tint and 3M security tint (based on what I was told). Here are my impressions of them:

1. Darkness: 3M darkest (quite dark), Llumar noticeably tinted but not too dark, V-Kool Elite appears clearest and many people thought the glass was untinted.

2. Heat rejection: V-Kool Elite and Llumar felt to be similar in heat rejection, ie very good. I usually park my dark-coloured car (V-Kool Elite) in the hot sun without any foldable sun-screen on the front dash, and the car doesn't feel super-hot when I return. 3M felt like poor heat rejection as the car (silver-coloured) was very hot under the sun, even in Cameron Highlands where the ambient temp was 27C. Driving on the NSE highway at noon required the aircon to be blasted at max to keep car cool. I was very disappointed as I expected better from 3M. Comparatively, the other 2 cars (V-Kool and Llumar) did not require any extra cooling (aircon set to normal levels) to keep the car cool.

3. SmartTAG: V-Kool Elite and Llumar - no problems at all. 3M - did not test

4. Garmin GPS: V-Kool Elite - appears to impede reception a bit, as I lost reception a few times, but this may have been due to being surrounded by tall buildings in the city; friend of mine said he experienced noticeably worse GPS reception when using V-Kool Elite. Llumar - appears better than V-Kool Elite, tested in the city. 3M - no problems with reception at all, tested in city and in the countryside.

5. Nighttime - did not notice any difference when driving at night.