Someone correct me if I'm wrong but linear light heads are bright head on and off axis due to the mirror technology in the light head. The TIR light heads are just as bright but only head on. They lose a lot of power off axis. TIR's seem to punch through heavy tint better than liner as well. Both though IMHO are very bright head on.
As everyone else has said, yes, use TIR for applications where you need only a head-on "punch", and use linear where you need all around effective light output.
I prefer to use linear products for surface mount applications and for intersection warning, where a wider range of warning is needed. For straight ahead or right behind warning (such as an interior bar, or license plate lights), I like to use TIR products.