It would not be a large, self-serving, self-praising organization like the JWs. It would not be an organization that claims they alone are the truth and all others are nothing, even while that organization itself has a history of error. It would also not be an organization that treats allegations of pedophilia in the manner that JWs and other large organizations, treat it.
Jesus would choose a humble non-denominational church that preaches the bible instead of boasting and promoting itself as the only true religion. It would also be an organization that truly cares for children and deals with those who abuse them, in a serious way.
The Jesus of the bible detests prideful boasting and the showy display of ones righteousness and the discounting the righteousness of all others as "nothing". (Luke 18:9-14) The Jesus of the bible hates the pharisaic practice of focusing on preserving image and outward appearances over truth, justice and righteousness. The Jesus of the bible also loves children and said woe to those who stumble such little ones.
The Jesus of the bible broke the sabbath law to show compassion to the sick saying that his father is one who 'wants mercy and not sacrifice'. He would certainly have choice words for the JW organization which advocates the opposite view, painting his father as one who wants sacrifice and not mercy, when it comes to the matter of blood transfusions. This is how you can know that the Jesus of the bible - if he exists - would not choose the JWs.