app design

Um, I don't see that you'd design an app in either of those. You'd use xcode. You could make picture resources in Illustrator or Photoshop. The best one will depend on the kind of pictures, and your preferences and experience as an artist.

Why don’t you try Sencha ? It is a good mobile application development platform with rich UI designs and cross-platform compatibility, that would make your app shine above the rest.