According to the latest study of app crash on mobile phone operation system by Crittercism, iOS faced more app crash than Android. The study has the chart as report after using 205 millions apps on 23 iOS versions and 33 Android versions. The result is quite shocking to me. iOS fails more often.
The worst case is in iOS 5.0.1. However it should be true since it is just the maturity stage of iOS 5.0 since with this version Apple has embedded many news features including iMessage, iCloud, Siri and many more. However with all of them running, it hurts the result of testing.
Personally, I have been using iPhone and Android for years already and I rarely have app crash on iPhone even after jailbreaking but mostly on Android.