Off the top of my head I can think of 15 people I know who have iPhones. Only two have experienced any issues. The first got a dodgy (hw issues not dodgy dodgy ) iphone4 which was replaced during the first week, the other dropped an old 3G this year and cracked the screen(yes that's 3G not 3GS)
We replaced both the front glass and LCD of the iPhone for £10 plus 30 mins of time following a YouTube how to
security wise, for an average user, the apple app store may be safer in the sense everything is vetted so it's less likely malware will sneak in (but it can happen). Android is easier to get malware onto the store but google do pull apps when they realise and with android you have finer control over permissions plus you're not tied to forever buying what your overlord deems suitable
Tl;dr Expect security flaws with any device, nobody is perfect. Apple's protects you from yourself a little more, android expects you to be responsible for yourself
Both decent devices, I'd be happy with either. Only phone I've used and disliked to date is the windows phone.
P.s I'm assuming you're on about the phone version not the tablet as others have mentioned.