On average, Android apps that passed through the company's cloud transaction, leaked user data in 0.3% of the cases, while that figure was 0.5% for iOS apps, yet the number there is derived from a larger sample. Both are not big numbers, though, plus it is mostly device info and location data that are shared.
Only a fraction of the leaked data was found to be personally identifiable info (PII). This is where Android and iOS differ again - just 0.2% of the iOS leaks included PII data, while on Android that share was 3%. The geographic distribution of the leaky apps is also pretty interesting - 70% of iOS privacy-related traffic comes from China, while for Android it's from US and UK. Not very surprising, given the come-and-go state of Google Services on Android phones in China.
iOS apps leak more user data than Android apps, but of the more benign kind