They both have there strenghts and bad things. I like both of them although they are both a lot different.
Android is a smartphone and tablet OS (operating system) made by Google. A few years ago, Google was only known for it's search engine, but not anymore! Google has been making new services like crazy the last years! Gmail, Drive, Calender,Google+... There OS is pretty much a mobile combination of all those services together. With Android, you can connect all your Google services with your smartphone or tablet. It's pretty much impossible to decide not to make a Google account when buying an Android device. It would be very stupid actually. When you're not wanting to do this, it's better to buy a Nokia 3210. Google makes Android phones and tablets in cooperation with Asus,LG, samsung,.. Those devices have a clean Android experience, that means there aren't any features aded or apps added. You don't have that clean Android experience when you buy an Android device that isn't made in cooperation with Google. There are a lot of companies that make Android devices like HTC,Samsung,Acer,.. and they ad an extra layer to Android. They ad features, change the UI (user interface) and ad apps. Every company does this in another way, I personally like HTC's 'layer' the most.
You can see, when you want an Android device you have so much choice! You can go for the clean Android experience or buy an Android device with an extra 'layer'.
IOS, by Apple is a lot different! When you want to buy an IOS device, you do not have much choice. When you want a tablet, you have to buy the Ipad. You can choose for an Ipad Mini, an Ipad with retina display or older versions of the Ipad. When you want to buy an IOS smartphone, you will have to buy an Iphone. The newest Iphone is the Iphone 5, before that there was the Iphone 4S, Iphone 4,... Apple chooses to be the only company to make IOS devices. When you have an Apple computer or other Apple products, the IOS devices are the best choice for me. They work perfectly together with Apple's features, you can sync your contacts,music,... just like you can with Android. But with an IOS device, you have to have other Apple products wich cost a lot to be honest. A google account is free! IOS, is a bit easier to work with and feels a lot more natural. Android has more customisation options.
I am a huge fan of both operating systems and I love them both! It just depends on what you already have, if you have a mac, go for an IOS device. If you don't have a mac, it's better to choose for Android I think because all the services from Google are free to use!
If you have any questions or you want to say something, let me know or email me at: firstname.lastname@example.org