Both the KTM Duke and the KTM RC are excellent motorcycles, but the better choice for a 5'6" skinny guy would depend on personal preferences and riding style. Here's a comparison between the two models to help you make a decision:
KTM Duke: The Duke series is known for its upright riding position, making it comfortable for daily commuting and city riding. The handlebars are positioned higher, providing a more relaxed riding posture. This could be advantageous for a rider with a relatively shorter height, as it allows for better control and maneuverability. The Duke models also tend to have a more torque-focused engine, which can be beneficial for low-speed riding.
KTM RC: The RC series, on the other hand, is KTM's sportier line of motorcycles, with a more aggressive riding position. The RC models feature lower clip-on handlebars and a forward-leaning posture, mimicking the stance of a supersport bike. This setup can be preferred by riders who enjoy spirited riding and track-oriented performance. However, the sportier riding position might not be as comfortable for daily commuting or extended rides, especially for someone with a shorter height.
Considering your height and preference for a comfortable ride, the KTM Duke might be a better fit. Its upright riding position and higher handlebars will likely provide a more relaxed and comfortable experience. However, it's essential to test ride both models if possible to see which one feels more comfortable and suits your riding style.