Many people are happy with the iOS 10, or at least those who have already tried it until now. However, it seems that many users’ interest has decreased after hearing the news about a jailbreak to be released for iOS 9.3.2. Thus, it is possible that most users will start considering downgrading their software.
However, you should know that there are two ways you can downgrade. You can use the clean and simple restore option, which wipes the entire data on the device and starts anew. Another option is the updating one, which lets you keep most of your settings and data.
Of course, there are ups and downs for each one of them, but as it seems, most people recommend the restoring option. Not only that you will downgrade your phone, but you also get the chance to clean your phone of all the data and previous settings. Also, it guarantees that the phone will work just as you expect it to.
Updating it may save some of your data, but not all of it. For instance, you will not be able to keep the history of your Messages or Phone app. Also, you might encounter some crashes with some of the apps, like the Music one. However, if you are using the iCloud, it’s easier than ever to restore everything back on the device whichever method you prefer (though you still can’t restore the Messages and Phone call data).
Keep in mind that if you already installed the iOS 10 and made a backup, you will not be able to restore the same backup on the downgraded version! If you want to avoid this complicated situation you should make a backup from the iOS 9.