Recs.
Updated
Specs
Pros
Pro Simpler to develop
The thing about developing for devices (particularly iOS) is that there are far less variations in hardware and software than the Web. No trying to handle all the variations of IE, Firefox, Chrome, Safari etc on Windows, Linux and OS X. Same goes for the APIs, no where near as many issues with things working or not working and it's rare in a mobile to have to do any sort of if-this-platform-or-that-platform style coding which I often saw when doing web work.
Cons
Con Uncontrolled software updates
It is posible to code your app to ensure users download the latest, but generally speaking your dealing with hundreds of thousands of installs which you cannot control. So if you have backend servers as part of your application, you'll need to have a strategy for handling different versions of your app.
Con Costs
Again depending on what you are doing, you may need developer memberships, device purchases, etc. Of Course web develop can also come with it's own costs too.
Then there are the development costs. On average, a mobile development takes longer than a web development. Although it's all going to come down to the skills and quality of the developers you have. Just because something is done fast, doesn't mean it's a good basis for a company. I've see companies start up based on a few weeks work and a couple of years later be in dire trouble because they kept trying to patch a hacked together product rather than writing a solid one.