</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">What diference does it make if you know where is it anyway ?</td></tr></table><span id='postcolor'>
In case they take you with the car/the keys off you etc - the theory is that if the fitters don't tell you where it is, you can't be forced to tell the thief, so he can't de-activate it.
Similar reasoning - you don't get a sticker advertising you have it, so they don't pull the car to bits looking for it.
IMHO, the one to go for is the system that alerts the company that your car has been moved without authorisation, ie without the ignition key. The other systems rely on you telling them your car has gone before the tracker is activated. If you've been away from your car for 12 hours or more it can be long gone - ie out of the country if you got hit by a professional team rather than a joyrider.