As far as 2ways go, I know if the thief unhooks or splits or cuts the power to the brain the 2way remote will ONLY show that the car isnt responding, it will not show that there is something wrong, and most alarm brains can be deactivated from the bottom of the car....
I also heard REGAURDLESS of a remote or an alarm all alarms are set by the gov. to deactivate if lifted to a certain degree ie. if your getting towed it will shut off.
So most car thieves have start just TOWING cars instead of breaking in. Towing them to a safe location and then just simply unhooking the alarm, jiming the lock and getting what they want. The entire car the system what ever, then they tow the car some where else and dump it or chop shop...
SO IMO BEST SECURITY IS!
1. LOCKING THE DOORS to deter optimistic thieves
2. INSURANCE put insurance on that shit so even if a tornado throws your car 100yards your good. =P