I'm just going to come out and say it - if you're the sort of person who uses a little padlock to secure the zips on your laptop bad or suitcase, you're pretty much wasting your time.
All it's going to protect your stuff from is honest people.
Now you might be thinking that the problem with padlocking the zip pullers together is an issue to do with the padlock, and if you fit a better padlock, you'll be safer. Again, you're wrong. It's nothing to do with the padlock, but instead an issue - a vulnerability, if you want to call it that - with the zipper itself.
Using nothing more than a pen, it's trivially easy to split a zipper open, grab the contents out of a bag, and then use the zip pullers to rejoin the zipper, making it look like nothing has happened.
This is why I carry my laptop and other valuables in a hard plastic case that's fitted with hasps. Sure, it's heavier and a bit more hassle, but it gives me much greater security against opportunist thieves.