What type or brand of car alarm is best or one of the best?

I am being offered the Auto Mate AM9 (2 way Auto Security/Remote Start System) but have nothing to compare it to. Is there anyone out there with user experience of this specific model? Can you tell me anything about it, please? Is it worth 9 (in the Northeast)? How much better is it than the factory-installed theft deterrent?

Thank you very much!:)