[saagarjha]

Add another six months to the S4's release date and you get iPhone 5S, which has the latest version of iOS and every security update that Apple has to offer.

[wor3q]

And also 20 to 30% slowdown when updated to iOS 11.

https://arstechnica.com/gadgets/2017/09/ios-11-on-the-iphone...

Same thing happened to iPhone 4 a while ago, it was literally killed by iOS 7.

I'd rather not update in this case.

Also, google is sending security patches for older versions of Android. Latest one for S5 is from beginning of 2018.