It seems that Utility application in Cocoa-Touch is just a simple application template for application with 2 views.
This is apparently good for simple apps which have primary screen and configuration screen.
Have a look at Understanding view controllers in Cocoa Touch which has some explanation.
It depends from what point you looking at differences. You still use cocoa-touch for your application. The difference is that simple view based application is a simple template for one screen application, you can extend it as you like. Utility application is simple template for an application with 2 views but you can extend it as you like.