The scale of a sculpture is the size of the sculpture in comparison to the viewer of the sculpture. We can come up with the ratio of scale (sculpture size / viewer size) which would be very important how we see the sculpture and how we would respond to it - in respect to how we see it.
We tend to have a different form when we look at the different sizes of the sculpture. If we see huge sculpture that has the same message by the artist as compared to the small sculpture by the same artist, we are most likely certain that we would have a different content as well as the subject matter for that piece of Art. We see the sculpture by the lights reflecting back from the object. If the object is huge, you have many more rays of light reflecting back to your eyes and it may, in general case, have a better and greater impact to you. But, we can't undermine the fact that if the sculpture was small enough to see it as well as feel it very closely would have better impact on how we respond to it. Hence, it is a matter of an individual and how he/she perceives the piece of art - big or small.
In my opinion, whether it is a large sculpture or a small one, they both have an equal probability of attracting the viewer and grabbing the attention. Large sculpture tend to seem more important that smaller one if we see from the perspective of its display in the common areas and accessible by many people. But, we can't undermine the importance of small sculptures with its mobility and closer look that give an opportunity for the viewers to feel it and get into that piece of Art. Therefore, both - small and large sculptures have its importance in their own way.
Viewing a sculpture is in itself an Art. Size really affects how we see a sculpture. The larger sculptures tend to have a larger impact on us in general term but, not always true. If we would have to view a large sculpture then we would have to walk around to different parts of the sculpture to see its form. We may observe one piece of the sculpture and certain content about the piece may come to our mind. And, after looking over all the parts of the huge sculpture, we can add up the form to make a combined meaning for the art piece. This may include us to drive around the sculpture or walk around it. But, if the sculpture is small, we can have a lesser time in observing its form and can make a meaning of it more quickly. We can feel the sculpture and see it clearly. We can make a holistic view of the sculpture and make a meaning which is one of the advantages of observing the small sculptures.