What kind of reality do we want to live in - a virtual or augmented world? Two of the most powerful men in the technology world disagreed this week on whether VR or AR was the answer. On Tech Tent we discuss which technology is winning. We also hear from teenage tech award winners with an optimistic view of women's place in the technology industry, and we meet the founder of Evernote who tells us why the world has fallen out of love with Silicon Valley.
VR v AR
Over the past couple of years, huge sums have been invested in virtual reality, with the promise that this time the technology is ready to enter the mainstream.
But while the likes of Oculus, Samsung, Sony and HTC have all launched headsets, sales have so far failed to match the hype.
This week Mark Zuckerberg unveiled plans for a new, cheaper Oculus headset - Facebook bought the business back in 2014 - and insisted that virtual reality was going to be huge: "The future is built by the people who believe it can be better," he declared.
At almost exactly the same moment Apple's Tim Cook was being interviewed at Oxford University and told a student that AR - augmented reality where virtual objects are imposed on the real world - was the future because it allowed a more human connection.
"I've never been a fan of VR because it does the opposite," he said. "There are clearly some cool, nichey things for VR but it's not profound - AR is profound."
One of those cool "nichey" VR things could be its use by businesses to help train people. We visited London firm Immerse which is developing products for the new Oculus Business division and is already working with companies like DHS and Inmarsat.
I strapped on a headset, picked up two handheld controllers and found myself in the middle of a desert being taught to assemble a satellite dish by a trainer who was in the next room but could have been thousands of miles away.
Justin Parry of Immerse says there is growing enthusiasm among businesses for the way virtual reality can cut the costs of training a global workforce, among other applications.
And surprise, surprise, he rejects Tim Cook's view that augmented reality is superior:
"AR can't take you to other places in the way VR can, it can't create the same degree of impossible that VR can."
Silicon Valley at the crossroads
"The truth is it's not that big and important a place in the scheme of things." That is what Phil Libin tells us about Silicon Valley.
The founder of Evernote, who is now running an incubator focused on artificial intelligence, is one of the more thoughtful tech entrepreneurs. When I talked to him about the change of mood towards Silicon Valley, with mounting criticism of its culture, he felt that it had always had an exaggerated sense of its own importance.
But Mr Libin says that lots of places have many of the things you need to build great technology - he gives Mexico City as one example - but haven't created a Facebook or a Google. What they lack, he explains, is the venture capitalists, the lawyers, the regulations that nurture small business:
"We have this talent in Silicon Valley for making small companies. We've exported that idea and somehow we got the whole world to believe that the real thing you have to do is make small companies"