This is not the Apps vs. Mobile Web debate.
What we're discussing is Server vs. Browser decisions about the mobile presentation layer. There are roughly two schools of thought (though lots of versions and variations) when it comes to mobile design philosophy:
Responsive Design - This is where you build a site that adjusts itself in the browser based on how big it is. On a small mobile phone screen, you may have some navigation at the bottom, big easy to follow text titles and large fonts for easy reading. However as you scale up this same code into a tablet or desktop experience, the presentation layer is shifted at different 'break points' and nav may move around, fonts become more appropriate for a larger screen and images fall into place.
Responsive design is also primarily happening on the client side, with the work being done by the browser.
Adaptive or 'Screen Specific' Design - This is a different approach. Designing for each screen is about creating an experience specific to what a user may need. Depending on the industry, this usually manifests as 'mobile sites for specific purposes' trading copy and elaborate image-heavy design for simple buttons, location-based features, click-to-call functionality (since they're on a phone) and that sort of thing.
This is typically handled server-side, detecting a 'User Agent' (the thing that the site uses to determine what browser, resolution, version, etc) and then serving the correct site, be it a mobile site or tablet or desktop or even Smart TV. For brands that want to control individual experiences differently, or simply strip away the web-chaff from the inter-wheat, approaching mobile design from this perspective makes sense.
So is there a right answer?
Different brands have different needs. Like any tactic, there is often a blend of both approaches depending on the user/audience, the product, vertical, as well as real business considerations like budget and speed to market.
Some brands simply let their customers decide. When Google says that 50% of searches are happening via smartphones, companies who pour millions into search marketing need to have an approach to acquisition through mobile. When analytics tells you that 98% of your customers viewing your site from a mobile device are using Safari on an iPhone, iPad or iPod Touch-- this should inform your strategy in the short term at the very least. Companies are still using giant Flash elements for promotions and even navigation on their sites.
So which factors are informing your decision making process? You can help by telling the Canadian Marketing Association what you think: http://4qr.me/cmamobile . It's a ONE QUESTION survey about your approach or philosophy when it comes to mobile design.
Andrew Kinnear is a member of the Canadian Marketing Association's Digital Council, and works at JPMorgan Chase managing digital strategy in Toronto. Follow him @andrewkinnear