Lightness depends on the size of the model. A large model with a higher wing loading will fly similarly to a small model with a low wing loading. Best to either ask specifically about a particular plane or just gain experience with different models so you know for yourself.

[link=http://airfieldmodels.com/information_source/math_and_science_of_model_aircraft/formulas/index.htm]Formulas for Model Aircraft[/link]