If you have a dark-colored car, definitely get a metalized-tint to block out the infra-red which HEATS up the interior. UV will also be blocked.
Unfortunately, metalized-tint is more expensive, and is a shield to radio waves (cell phones), and reflects back like a mirror to others.
If I had to do it over again on our black W124 wagon, metalized-tint would be it.
PS: there's a CLEAR European film that blocks InfraRed and UV but it is VERY expensive.