An Apple Locks Tighter Than a Droid
Apple iPhones have a definite security edge over Android phones. Because droids can only use Full Disk Encryption each time a passcode lock is entered it remains in RAM until the phone is rebooted.
iPhones can also use file based encryption which lets them be more tightly secured as soon as they are locked. Some data can be accessed before the phone is rebooted, and so the keys don't have to stay in RAM.
Androids can employ ARM TrustZone which forces encryption keys to be derived from the device itself making offline dictionary attacks more difficult.