Bin Laden had an engineering background.
The choice was symbolic, it's true, but he knew that the Empire State Building was built far more solidly than the World Trade Center. Both buildings naturally exceeded the required load-bearing capacity, but due to limitations of some of the construction materials used, this is how the Empire State Building was built.
This is the Empire State Building under construction. It's all steel. You can see the beams extending from the top to support the future floors. There's a steel column roughly every 2.5 meters throughout the structure. It's also covered in masonry.
In comparison, here is the construction of the World Trade Center.
The core of the building features beams every 3.5 meters, but most of the building's structural strength is located on the exterior, which is constructed as if it were a solid steel box. From the architects' perspective, this was an advantage, as it allowed for significantly more open space within the building.
There's no masonry on the exterior, just steel and glass. The steel is very strong, but there are windows sandwiched between the steel sections.
In fact, the Empire State Building had already survived a collision with an airplane.
Yes, there was a fire, but because the interior walls were lined with masonry and the floors were concrete, the fire never reached the two floors directly impacted by the crash. The building was repaired to like-new condition.
Thus, even a heavier plane would not have brought down the Empire State Building - it simply had too many redundant supports.
Afterwards, Bin Laden did not expect the towers to collapse (it was lucky for him), but he expected, because of their construction, that the damage would be much greater and that the fire would spread more, which happened in both cases.