Yep it seems a choice between the cheaper 3M or the more upmarket FSK. 3M has the tinted stuff, FSK has the whole range of tinted up to mirrored. I have two small children so I want to keep the heat out as much as possible while still being able to see at night!
Supposedly some of the mirrored stuff blocks EM signals so GPS and electronic toll system can be affected, but they can guarantee it won't interfere and give a 3 year guarantee.
I also want to keep UV out as I have fair skin sensitive to sun damage (very Taiwanese I know