Nicholas Carr is a technology writer and the author of The Shallows: What the Internet is Doing to Our Brains. On a recent Motley Fool Money Radio Show, Chris Hill asked him about the relative merits of Apple (Nasdaq: AAPL) and Google (Nasdaq: GOOG). This is the second of two parts.

Chris Hill: One of the emerging rivalries that we can't help but watch constantly is Google and Apple. If you had to bet on one of those companies over the next few years, which would you bet on, and why?

Nicholas Carr: I think I'd probably bet on Apple, simply because I think it has a clearer idea of what people want across software, hardware, and Web-based businesses. And I think it has proven that it can remake markets around the power of its own products. 

When I look at Google -- for all of its talents -- it seems like a more passive kind of company. It throws out a lot of things on the market, and then waits for the response, rather than getting out ahead of what users and buyers and searchers want. And as a result, if you look at its business, it's obviously a very profitable and very successful company. But it's still a narrow company. It does all sorts of things but it still makes all of its money selling little tiny ads next to search results or next to the content. 

So I think Apple right now shows that it can succeed across the much wider range of activities than Google has proven itself capable of succeeding.

Hill: Other than each other, what do you think is the biggest threat to Google and to Apple?

Carr: That's a good question. I think it's probably the unanticipated service that comes out from an entrepreneur. 

Google seems to be the most vulnerable, simply because it is a narrower company. I think that the quality of their search results has lost something as it's bringing in more and more things like video, Tweets, and news headlines into its search results. So I think it could be more vulnerable to a completely new way of navigating the web and navigating the information. 

Apple is a tougher call, because right now, it seems to be going from strength to strength. But if the mobile market ends up proceeding the way the PC market did, when Apple lost the PC market, and if we go with a more open system and reject the closed Apple universe, then that would obviously be a big hit to Apple. There is no sign now that we are moving in that direction. But it's always possible.

Is Google making you stupid? Find out in part one of our interview.