Which to build: Native or Web iPhone App?

I am here at iPhone Dev Conn in sunny San Diego and just wrapped up my lightning talk on the hot debate of whether to start developing a native iPhone app or mobile web app. I feel strongly on the subject and it seemed like most attendees here liked the idea. So here it is...

Q: What do all of the Top 10 iPhone apps have in common?

A: Web Services

That's right, they all have services hosted on the Web that are really what give their app value. OK, we could stop the discussion right here and say, go web or go home. But let's dive in deeper to bring some clarity on the subject.

First, I will admit, building a native app is absolutely the best solution in the end. Nothing we build on the Web will compete with a native built app.

Start With a Mobile Web App

I propose-when starting to build a new app-you should first build a Mobile Web app and then focus on building native apps for individual platforms. Obviously, if we are going to create a quality mobile app, we need a complete Web service API. So even when doing native development, you have to start with the Web! So, build your data/business models and create services for them. While doing this you will be working out issues in your logic, and most likely come up with brilliant ideas for your UI.

Now that you have the infrastructure you need, the app itself is really just a View. So why not start developing it in a language you already know, HTML? It is much quicker to create a Mobile Web app with your existing knowledge than to start from scratch in Objective-C. Not to mention, when you develop on the Web, you are already targeting countless platforms. The Mobile Web app you created will give you a cross-platform, fully functional, and in production application much quicker than any native option. This really is a great way to buy time for focusing on creating high quality native apps that not only target single platforms, but utilize them fully as well.

Another advantage of starting with a Web app is that you will be getting your feet wet with the new paradigms of Mobile architecture, without having to learn a new language. This will help you focus on the bigger picture of your applications usability. You will also find holes in your UX and probably come up with new concepts to apply when you build the native version.

Build Them Both

Native iPhone apps and Web iPhone apps are not mutually exclusive. Almost all of the Top 10 apps in the AppStore have both an app and a very similar Mobile Web app. Which one do you think they built first?