What was written above still holds true! Which framework to use depends mainly on the following:
* Have you worked with Objective-C before / with ActionScript 3 before? If you haven't used any of them, AS3 will be easier to learn. Otherwise, stick with what you know.
* Do you want your game to be cross-platform or iOS only? Starling works on Android, iOS, and the browser, Sparrow only on iOS.
* How much integration of standard iOS libraries do you need? GameCenter, iAds, etc., can be used in Starling as well, but this will be easier in Sparrow.
Performance-wise, there's not much difference between the two frameworks in their current versions.