-It was effective because Jesus would experience what the human experience is ,so that as a judge,he would kow what it is to be human.

- he was the only one who had been to heaven,and would be able to tell the world the truth about the father,since he is the one who knew the father personally.

-He practically demonstrated his love for the world- Jn.3;16.

Since the father and the son are one,then  the people could clearly see the attributes of the father in the son.

-God could not achieve the plan for salvation without a human /physical sacrifice,and hence,Jesus had to come in the flesh so that the sacrifice  to seal the covenant between God and Man, which is always sealed in blood ,could be accomplished once and for all.