Having used both Cortana and Windows Phone quite heavily, I find these adds pretty humorous. The truth, at least in my opinion, is that Cortana unfortunately has a long way to go before it catches up with Siri. Any comparison between the two that seems to end up in Cortana's favor is a bit of a joke.
I don't say this from a perspective of simple bias; I used Cortana for about a month in the developer beta releases... which was only about 3 months ago. And I found Cortana to be so frustrating to use that it bordered on being a useless feature. Among the annoyances of Cortana was the fact that there was no equivalent function in Windows phone to asking Siri a question from sleep. With win phone, you had to wake up the phone, enter a passcode (if you had one set), and then tap the Cortana or search icon in order to ask a question. And that series of actions made the feature almost useless when engaged in any activity (driving, walking, etc) where one might expect to actually gain value from it. The lack of a real button on windows phones can be seen as a true liability here, since Apple has been able to leverage it for so much.
One positive for Cortana is that it is not simply a voice assistant - Cortana doesn't have to speak at all, and is wired into almost every search activity the OS presents. But that feature spurred two more annoying issues. First, when Cortana was active (e.g. configured to be enabled), every search enacted by the user is routed through Cortana, and if Cortana is down (which it was a LOT), then you just plain couldn't do a search with Bing at all - you had to open a browser, navigate to Google, then do your search. And Cortana would not work across WiFi - only using the phone's cellular connection. Which made it pretty useless when you were deep in the bowels of some building and wanted to know if there were any good places around there to eat. Now, if a developer had these issues, can you imagine what Grandma would do with these issues?
Basically, I think the Cortana implementation is flawed, and lacking in attention to detail... and unfortunately the details that were missed are the ones that take features like this from the gimmick to the useful category. That is of course my opinion.
Maybe MS will fix these issues - maybe they have already. But at the time, I came away from Cortana thinking it had really no chance at all of competing against Siri.
Edited by Thomas Tupper - 9/2/14 at 9:41am