The difference between a Tracker and a GPS type system (such as Quartix) is that if a vehicle loses satellite lock, which it will do inside a garage, it becomes untraceable (though you will have a log of its position until it's put in there, but a van can cover quite a distance in a minute between fixes). A Tracker, on the other hand, once switched on, will be trackable pretty much anywhere it ends up (even if it's put in to a shipping container, which used to be enough to block the signal in the early days, I believe).
I'm not saying one is better than the other, just pointing out the difference.
Vin