I had the "spray-on 3M clearbra" applied to my 335i by Crevier. (local dealer)
I was told that this was superior in terms of protection and longevity than the film option, not to mention no visible line delineating the bare paint versus the filmed section and no discoloring or "yellowing."
They sprayed the Hood, made film pieces for the headlights, and sprayed the front bumper. This happened last Summer. After ~5-7k mi., I started seeing the road debris impacted dotted chips on the front bumper and the hood. I think it was around a $1000. I was NOT overly impressed by the product. It does help, but it is not a shield. Like Technic said, some impacts will tear through the clearbra.
Needless to say I won't be getting black again any time soon.
Hope this info helped...
2013 E92 M3 Individual
Sold: 2011 E92 M3 SSII | Sold: 2008 E92 M3 SSII | Into a Wall: 2008 E92 M3 SSII | Sold: 2007 E92 335i JB