They don't bother with the chain - they use the boltcutters on the padlock. Only one cut and you're done !
In my opinion the best type of lock would be a thick cable lock with a large combination lock too big to fit most boltcutters. Sure you could still cut through the cable, or break the lock by twisting it between two big pairs of pliers - but how long would that take ? Most thieves are kids going out with Dad's boltcutters, or people on their way home from the pub.