In fairness, the slot in that one the guys is breaking is massive, mine is the same thickness as a brake disc and the 'reach' is much shorter too so much harder to get something in the 'rear' end of it. That being said, I don't use it as a way of securing the bike, for me it's just a quick and easy visual deterrent for opportunistic thieves.
At the end of the day, if someone really wants your bike (or car etc.) they will be able to take it but if a disc lock, chain etc. makes them think twice about doing it then you're at least mitigating some of the potential chance of theft.
I don't really see the point in alarmed ones, again, if they are going to take the bike then chances are the alarmed unit won't stop them or it'll make them damage the bike in spite.