I would say your biggest issue isn't as much your operating system as it is the network you use your device on. For example the most secure device in the world can be used at McDonalds open wifi and have its info intercepted....and it's not your device's fault rather the connection. Any security program is only as good as its weakest component.
THe iOS operating systems are still very secure because they are highly resistent to viruses and malware....but a user can still click on that 'you won a million dollars' link in an e-mail and hand their personal info over to a hacker.
If you feel you can no longer trust it, then stop using it. But I would say a user's internet connection and behavior are larger security vulnerabilities than any device.