The price of the material can vary by over 3:1. What I ended up with on my vehicle was a top-end tint from 3M. At a 70% material, it has better IR and UV ratings than most all other tints with much darker tints. It is also the max you can have in some states and still pass inspection. So, some of it depends on whether you really want dark, or you want something that looks good, but isn't!
http://solutions.3m.com/wps/portal/3...omotive_Films/
Mine's only been on about a year, but no scratching, bubbles, loose or other visible defects. The difference in interior temp was dramatic when sitting in the hot sun.