The non Google Play stores are severely nerfed though - they for example can't auto-update apps installed from them, like Google Play can.

So if you install something say from Fdroid and want to have it up to date (say a Firefox rebuild), you have to periodically open the Fdroid app, check if there are any updates for the app and manually install them if there are some.

Also I don't think you can currently hide Google Play if its installed, again giving it an unfair advantage.