According to the Netbiscuits blog…
The main advantages of client based mobile Web applications are that they provide very good possibilities for graphic design of user interfaces and keep content available even offline. Furthermore, they often show faster reaction times and are sometimes easier to link to other telephone functions such as directories, camera, etc. The main disadvantage of every client-based solution is that they initially need to be downloaded by the user and installed on the mobile – a practice that will need to be repeated for every new release. Many users are prevented from taking this step due to technical problems, security issues and a lack of clarity concerning costs involved. Furthermore clients are always dependent on the mobile phone operating system and must often undergo costly adjustments for each individual terminal.
Mobile sites, on the other hand, do not require any installation. They are immediately available over the browser and the sites’ content and software are continuously updated unobtrusively to the mobile user. Mobile sites also provide a greater scope of outreach than clients do, as nowadays practically all mobile phones have a browser. Adjusting mobile sites and rich media content to various mobile terminals can be made 100 percent automatic. This means a massive reduction in development and testing expenses. User interface design is also no longer an obstacle. Modern mobile phone browsers enable use of AJAX and Flash, thus creating a user experience similar to that of PC Web. If a company is looking for a larger audience reach with as little hassle as possible, the mobile site is the clear winner.
I totally agree. The one thing that I advocate is to have some kind of markup language that allows the browser to have access to native device functions such as the PIM, camera, etc.