I've built a lot of apps, from really simple ones to incredibly sophisticated ones that took many developers. All of them were built in Xcode.
If you want to make a painting, you start with a canvas, and in the iOS world, the best canvas is Xcode. There are other solutions (phone gap, xamarin, etc.) but in all honesty the best for iOS is Xcode. You always have the latest and greatest at your fingertips, even on day 1.
The other IDE's (phone gap, cordova, xamarin) always put an additional layer between you and your app. It slows things down and adds additional complexity. The benefit of compatibility for other platforms is, in my opinion, outweighed by the drawbacks.