Not allowing third party stores in the Store is a security feature because they can install APKs that have not passed through Google's security scanner.
Google does not prohibit you from installing third party stores.
Also, how are they using their dominance for search and browsers to do something? I can install Firefox on Android, I cannot install Firefox on iOS. I can do "Hey, Cortana" if I install Cortana on my Android phone and do Bing searches, but not with iOS. I can install the Bing app and get a launcher widget to perform searches with, just like I can with the Nexus Launcher's integration, but not with iOS. I can change the launcher out entirely, I can't on iOS. I can replace the lockscreen, but not with iOS.
And as for taxes, Google paid the taxes that was required of them by Ireland. The EU thinks that they can post-facto change the law to effect Irish companies. This is illegal and immoral.
This is also what the founders of Google have complained about, that US companies can do this, and are forced to do this by their shareholders. They are being punished by the EU for not following the status quo and being made an example of.
So, explain to me, again, how Apple is the bastion of user freedom? Android is a shit OS, but at least it allows me to run whatever I damned please.