A kill switch will make it harder to steal the car, but will do nothing to protect contents. If someone really wants to steal my car, they can have it. I'm not that attached to it
As for suggestions, I work for a company that makes alarms, remote start systems, and etc. (We even made/built the add-on alarms that you would have bought from the dealer when your car was brand new). So for brand preference, clearly I have a bias. But as I said before, even the best alarm in the world isn't worth squat if it's not installed well. My generic advice would be to seek a REPUTABLE car audio shop to you locally, and see what they have to offer. I'd take a $50 alarm with a great installation over a $500 alarm with a hack-job installation without hesitation.