This is a little bit difficult to answer because the legislative and executive branches are so intertwined that it is hard to speak about them separately. In a parliamentary system, the ministers are members of the legislative branch as well as heads of ministries in the executive branch. For this reason, the best answer to your question is that the legislative branch is better able to represent the interests of citizens.
In such a system, the legislative branch is both more powerful and more democratic than the executive branch. Only the legislature is elected, which means that the legislature will be more responsive to the needs of the people than the unelected bureaucrats are likely to be. In this system, the legislature also provides the ministers, which means that it also has relatively strong control of the executive branch. This makes it more able to respond to the needs of the people.
In this system, then, the legislature is more likely to pay attention to the needs of the people because it is elected by them. At the same time, it has more of the power needed to effectively respond to the people's needs. Therefore, it is the branch that is more able to represent the citizens.