Users are spending more time using native apps than web apps on their smart phones. However, this trend will reverse in the near future as the web becomes ubiquitous.
According to a recent survey about two-thirds American smart phone users' time is spent on mobile applications (the other third spent on web applications). Even you use a 3rd party framework like mono, to develop a mobile app you will be forced to rewrite significant portion of code in order for your app to work on each specific operating system (Android and iOS). Therefore one could argue that even today, web applications gives you access to a bigger market overall with one single code base.
Mobile web browsers are perfectly capable of most functions, however some low level phone features aren't accessible. Mozilla is taking a leadership role on this front and actively working on a cross-platform programming interface that will fill-in the gaps. We hope an app-store isn't far behind as well, since that would be the last real hurdle to wider acceptance. Without a centralized distribution centre that makes app installation safe and easy, web application growth could be hampered. Much like open source software, it could be relegated to a small but enthusiastic group of geeks.
Also keep in mind that data plans are still very expensive in parts of Canada, so some users might be reluctant to make extensive use of web based applications. But the trend is moving toward free Internet (Wi-Fi) everywhere, so if carriers don't lower prices there is always a plan B. From personal experience, with wireless Internet at home and at the office, as well as my favourite restaurants, I make very little use of 3G.
The trend is clear, web based applications offer enormous advantages today, and even more-so in the near future.