The main difference between the two OS is the Android is the most open source of the two. This gives the added benefits of more customisation option and easier development for games programmers. This is mostly because it is based on the Linux operating system. IOS is more restricted which is better for security but will also make it harder for games business to get their games on the app store which is the equivalent of the google play store.
Both operating systems stores have to go through a process to get their games on the stores. How apple is more protective about what is on their stores. This means it will have to follow the guidelines and terms of service. There is also a fee for uploading your game. For Apple this is a $99 a year charge buy on Android the is only a $25 charge per game. Each system has its benefits. For IOS this is the fact that users with IPhone are more likely to pay for app and in app purchases. For Android this is the fact that a larger amount of users has them, this means that your app will reach a larger audience.
In terms of development Android has the upper hand. This is because games can be made on almost every engine and can be exported as an APK which is the extension that Android uses for apps. As the user of Android are less restricted then IOS these APKs can be downloaded and ran even if they are not on the play store.