It totally depends on your goal. If you want to immediately disrupt all communications, financial transactions, etc in preparation for an attack, you probably want to crash a lot of those machines (and by crash of course that means disable, not just reboot).
An the article already said it was a particular 48,000 machines that ended up taking down several South Korean TV stations and banks. 1800 "soldiers" taking out significant resources in South Korea near instantly? Sounds a hell of a lot more effective than anything 1800 (or 18,000, or probably 180,000) North Korean infantry could accomplish.
Also, please explain to Sony Pictures how the North Korean cyber warfare group is just propaganda. While it's not proven yet, signs are pointing to that group being responsible for completely taking down almost all operations at Sony Pictures for the last week, as well as stealing several high def copies of upcoming movies. Probably cost them tens of millions of dollars so far, maybe more.