How is Quick Weld different from Use Thresold when importing stl?

Question

3ds Max

How does Quick Weld differ from Use Thresold when importing stl, except for the time to import?
For example, with Quick Weld, importing takes 20 seconds, and with Use Thresold, more than several hours.
The number of polygons in both cases is the same, visually they are the same.
There must be differences with such a difference