It comes down to luck of the draw. I've travelled internationally a number of times with both a full sized bike case and an S&S case for a coupled bike. Neither seemed to be more likely to be opened and I'd say they got opened 10% of the time.

One funny story with the full sized case. I had the bike plus a bunch of other stuff (helmet, shoes, shorts, jerseys, etc) packed inside it and it weighed a ton. I was there when it came off the unloading ramp in customs. Two TSP guys, one big burly guy and another who couldn't have weighed 100 lbs soaking wet. The bike guy says to the little one "check that one". Little guy picks it up (barely), grunts it over to a table, stands there a second until the big guys back is turned, stamps "inspected" on it and sends it on its way.

So much for security.

Keep in mind that big heavy cases really piss baggage handlers off. I saw one lift mine up to shoulder height (really hard to do since it was both heavy and bulky) just so he could throw it onto the tarmac. If it's heavy it had better be well packed.