In which of the houses is colder in winter, if the area and thickness of the walls, as well as the heat sources, are the same?

It all depends on the thermal conductivity of the material from which the walls are made.
Example: One of the houses has walls made of bricks, while the other is made of wood. A brick house will be colder in winter. Brick has a higher thermal conductivity than wood. Therefore, in such a house, heat loss is higher, which means it is colder in winter.