Where Least Secure, Android or iPhone?

Popularity of a mobile operating system is not always better, especially if potentially invite attack by cyber criminals. Currently, the operating system for mobile phones is the most popular Android and iOS in the iPhone.
Now, which of these two operating systems are the most vulnerable or least secure?
To find the answer, Sourcefire security research institute conducted a study titled "25 Years of Vulnerability" which was released in March.
His research is quite surprising. iPhone turned out to contain far more vulnerabilities than other mobile operating systems, including Android.
Yet all this is always referred to as the operating system is the least secure because it brings the open source Android.