It's difficult to have a real comparison because Android comes in many shapes and sizes but also each OEM tries to tweak it to make it more unique. However there are some things that you can compare.
iOS has always been very easy to use. There isn't a lot of customisation and as a result everything is in its appropriate place. Every app is on the home screen, every setting is in the "Settings" app. iOS has also been far more efficient than Android since Apple can tailor its software very specifically to the hardware that runs it since Apple make both. iPhones also have the best touch latency of any phone. When you touch the screen it's like the object you are moving is moving exactly with your finger. With all Android devices it's always at least a little slower.
Android however offers a lot of customisation on the home screen. You can even change the home environment entirely by getting a different launcher from the play store. Notifications are also far superior on Android (especially on Nougat). You can reply to multiple threads in one bundle (e.g. if you have 3 emails bundled from one app you can expand them and reply to each one individually without entering the app).
Then there's also Google Now vs Siri. This again is generally where Google Now is cigarettes considered better since it's very good at obtaining information (it's Google after all) but lacks the personality of Siri (the jokes, the answers to silly questions).
I've barely scratched the surface of what the difference is between the two OS's but they're both great in their own different way.