I regularly use both Cortana and Google Now, and I found the article to be quite accurate. GN is generally a bit faster, more accurate, and more comprehensive. However, it does lack a couple features of Cortana.
Google Now is also much better at prediction, giving you information when you need it. Flights and package tracking are very reliable, unlike Cortana.
Cortana and Siri gets big brownie points from me for their personality though. It's something I miss when using GN. It's not really useful as a tool, but it adds something to the experience. GN has a tiny bit of it, but nothing like Cortana or Siri. It makes the assistant seem more real.