Ios is much more secured than Android that's why is more costlier too,also it's a brand only Apple users use it operate with it and it's very much secured in such a way that it can be rendered useless if stolen,but Android has lots of competitors
For me, by looking at the general perspective. IOS is way more secure than android in the sense that IOS is intentionally made for apple users "ONLY". No other brands of phones can use this operating system where as with android, there are a lot of phones having this OS which means it becomes a competitive place for people wanting to abuse the system.
Well to the best of my knowledge, it's simply because IOS isn't open source, but android is. This means that the IOS source code isn't released to the public like how Android is and as such hacking into an IOS device is next to impossible.
IOS is as rigid as they come and as a result it's almost impenetrable. Android on the other hand is open source and that's why you are alot of phones these days which all have different skins on top of the android OS.
The fact that IOS isn't open source is what makes it so secure. If you are going to use an iPhone that you just stole then you'll probably be found and tracked within 24 hours, the best thing you can do is sell it part by part because there's no way of unlocking that phone or its iCloud without knowing the original owners password.
I hope this helps