I should explain that this choice is not available to everyone. It applies only to children adopted by Canadian citizens. Permanent residents who adopt children do not have this choice. There is a second category of people for whom adoption is not possible in the country where the adoption takes place. These people can gain custody and then complete the adoption process in Canada. In that case, the child is not yet adopted. A fairly large percentage of people are in this situation. So we need to keep both choices. There are countries where it is not possible to adopt a child in certain situations. I myself adopted a child in India. I could not complete the adoption process in India because I am Christian and only Hindus can adopt. There is that sort of restriction.
The difference was not created deliberately. The two choices parents have are more or less the same to us from a bureaucratic standpoint. There are not really any advantages or disadvantages.