When I bought a MacBook Air earlier this year, I promised to download as few applications to it as possible. I had noticed over time that my MacBook Pro struggled under the weight of apps like DropBox and Evernote. It would be a test of the progress of web apps. And it this experiment has come to show the contrasts between mobile and desktop use.

I haven’t installed many apps on the Air. Microsoft Office, Textmate, Chrome, TextExpander, Alfred (an essential launcher) and 1Password for managing web accounts. These are all bare bones and essential.

My only indulgences are Sparrow, the GMail companion app, and Reeder, an RSS reader with built in Readability. I use Dropbox and Evernote exclusively on the web. Expenses on Expensify. Blogs on WordPress and Tumbr. Google Docs and Presentations for sharing. Salesforce for CRM.

On my mobile phone and tablet, it’s been the opposite. I only use applications. Pulse, Flipboard, Mail, Maps and so on. I rarely visit a web page in the browser on the iPad.

These two experiences are quite different. In most cases, I use different applications on different platforms to do the same things. Pulse on the iPad, Reeder on the Mac. Mail on the iPad and Sparrow on the Mac. I’d love to have the same experience on both, but in most cases, it’s not yet possible. Not to mention I carry an Android phone, so forget about using most of these apps on the go.

Cross platform use is the biggest driver of conversion to paid users in freemium and premium businesses. At the Freemium Summit last year, Evernote reported 39% of cross platform users convert to paid. And we’re seeing similar patterns in our companies.

Serving users across platforms with comparable experiences is important but expensive and requires a well designed API architecture where apps, both client and web, mobile, desktop and tablet can all use the same core code base.

Because of the costs involved in supporting these distinct platforms in planning product roadmaps and hiring engineers to build the software, I think we will see a shift to a less expensive, more scalable solution: HTML embedded in native applications. Facebook has begun to implement their apps this way. Google is doing similar things as are others.

Building client apps that use HTML ensures that code is reusable across platforms, enables A/B testing and is standards based. Lastly and most importantly, apps come to market faster.