In such a system, there is so little difference between the legislative branch and the executive branch that it is hard to say that one branch is better able to represent the interests of the citizens. If we have to choose one, it is probably more accurate to say that the legislative branch is better able to represent the citizens.
The reason for this is that the legislature is the source of the heads of the executive branch's ministries. The men and women who end up in the cabinet all come from the legislative branch. This means that the legislative branch has more power since its members also serve (some of them) as ministers. The legislative branch is also more representative because it is elected by the people.
So, in such a system, the legislative branch is more able to represent citizens because A) it is elected and B) it is more powerful than the executive branch.