From the design point of view, what is more important to be ashieved, spectacular form or functional applicability of the construction object?

The answer is situational based on costumer requirements and some time you need to dig deeper into the customer back ground to identify his or her main interest.

The designer will look into it  from different view:

An artist designer would be trying to encourage innovation in the design structure that reflect his or her signature style.

other designers will try to make it more functional and efficient.

but i would say a lot of designers will try to make something spectacular, out side or inside the construction.

Spectacular form, cause your question is more of a visual aspect of the design not the functionality. and spectacular form is mostly the key of winning the project cause people are more visually stimulated by wow objects.

Sincere and nicely elaborated