Keep in mind that just because the lock/chain CAN be defeated, doesn't mean it can be done quickly or quietly.
I mean if it takes an angle grinder a minute to hack through the lock...then yeah a thief with an angle grinder can steal your bike.
But if you park it in a populate area with lots of witnesses, no one is going to spend 1 minute with a noisy spark throwing attention grabbing angle grinder in front of a lot of witnesses to steal it. If you park if out back behind the dumpsters....well not that being robbed is your fault, but you did make it easier.
As for picking a lock....it's quiet. So someone might be able to go unnoticed for 5 minutes as passers by will think he's just tinkering with his own bike and wouldn't notice he's messing with the lock. But how many thieves are going to spend 5 minutes stealing your bike when the 3 bikes next to it are tied up with a Wal Mart chain, a bungee cord, and unlocked entirely? A kid stealing a bike to take a ride or the drug addict looking for a quick flip are going to go for the low hanging fruit, not the one that takes work. Most wouldn't know a quality bike from a POS anyway.
Now the professional who can identify a quality bike and has a means of selling it quickly....that guy is your real enemy here. That is the guy who are really trying to defend against with the harder to bust lock. Problem is that guy knows what he's doing. If he wants your bike, all you can do is slow him down. You can't stop him. BUT!!!! slowing him down may be enough if you make it take long enough to steal it that he risks being noticed.
That means reducing the amount of time he has by parking it in a well it area with witnesses. And increasing the time to takes with a better lock.
The single best thing you can do or bike security is to make your bike take longer to steal than the bike next to it.