How do the simulators (reflex xtr or others) compare to real rc flight ?
Easier, more difficult or just not comparable ?
Sims tend not to be the same as real flying. Wind conditions, distance, how fast the plane moves - it's not quite the same.
That said, sims DO help establish the proper orientation for flight - i.e., getting used to left being right and right being left when the plane is coming towards you, or practicing inverted flight where down is up and up is expensive in real life. It also helps you to get the basics of flight down, and help you learn muscle memory for left and right, up and down, etc., without costing you an arm and a leg every time you crash (and you WILL crash).
I will use a sim to practice things like harrier maneuvers or knife edge flight for 3D flying (something I'm still pretty terrible at), or for practicing when it's nighttime or there's bad weather. There are certainly benefits; just don't expect things to behave exactly the same way in real life.