It is a misconception that trainers are easier to fly. Like bicycles with training wheels, trainers are harder to crash, but once you have some basic skill they are not easier to fly. To the OP and anyone else considering this question: if there is someone at the field who will let you buddy box with their stick or 4 Star, go get yourself a taste of sport flying. Nothing is easier to fly and control than the classic "2nd airplanes," although they are easier to crash because they aren't designed to save you from yourself. What I've learned is that to build piloting skill, you need to be flying the airplane that makes whatever skill you are working on the easiest. So if that is flying the circuit and landing, then stick with the trainer. If it's loops and rolls, then a more neutral handling plane is in order. The one exception to that is not to use your first flying season time on a build. If you have basic control down and already have a sport plane, then don't be afraid of it. But if you will have to take your hobby time to put one together, then continue learning on your trainer as best you can until winter.