Trying to create a passive income. Should I create a web app or a mobile app?

I am looking to create a passive income stream. I have the skills to create both web and mobile apps. But I have been reading that making money from mobile apps is really hard and most iOS apps don't generate much revenue.

So should I focus on creating a web app instead?

Can anyone confirm if iOS apps aren't very profitable?

It's very hard to make any money passively anyway. That being said, I think it's easier to generate some income from paid apps on mobile than from web sites. Charging anything on the web is hard. So if your goal is a small passive income, I'd go with the app approach.

It seems like a few mobile developers are able to live from ad revenue and some are even very open about it. Take a look at this developer's revenue reports, for example: http://www.indie-story.com/reports/