Which (Official) Arduino IDE to use? I have bought an Arduino UNO that turned out to be the Italian version (Arduino SRL) not the American one (Arduino LLC).

Now when I go to arduino.org and arduino.cc, they both have different versions of the IDE!

So, which one should I use (if they are even different) ?
You can use both IDEs no matter of the origin of the UNO even fake ones runs with the IDEs.
The arduino.org IDE is just a fork of the arduino.cc.
But arduino.org has many Board which are only run with the .org IDE.