Here is my 2 cents,

As stated before, all are equally hard. However, in order to be proficient at any you must first learn the basics. If an average pilot wants to take a giant leap in flying skill he MUST learn to use the rudder properly. If you take the time to learn this, everything else will fall into place. I don't know how many times I have seen someone take off at full throttle, and not touch the left stick again until it is time to land. If there is a cross wind blowing in, they usually end up landing in the pits. It has taken me a year to get halfway good, and I still have to think about rudder correction when inverted.

Greg