I haven't tried the others but I can highly recommend prey. You only have to subscribe once your laptop goes missing. Its also open src so I believe you can setup the serverside yourself if you're worried about prey being hacked.

It does have a few small bugs, and one thing I didn't like is the 100 report limit. You see, the 100 rpt limit means that if you want to do 2min monitoring you have to really keep on top of the reports.

Overall 2 thumbs up from me for prey.