to me...no difference

#1 asks whether you want to (go) or not. #2 asks if you want to go. Pretty much the same, really.

only a little difference.only accent on where or whether. #1 base on have been knowing somebody want to go to beijing ,but not sure. #2 base on don't know whether to go or where to go.

#1 asks whether you want to (go) or not. #2 asks if you want to go. Pretty much the same, really. This is right!!! it is different.~ listen to the first one! this is right!

你要不要去北京？the sentence has an optional sense asking whether you are willing to go to beijing (with the asker),moreover,it is a normal question without any connotation indicating the asker's surprise when hearing someone is going to beijing.你要去北京吗？this sentence has a gentle sense of surprise when the asker hearing he or she may go to beijing?also it seems the asker cares about him or her because the asker worries what it would happen after he or she's arriving in beijing