Inline Extractor fans can be used to either push or pull air, depending on their orientation and the desired airflow direction.
When pushing air an inline fan overcomes resistance from the ducts or other obstacles in the airflow path, such as filters or grilles. When air is pulled through a duct or ventilation system, it can create negative pressure within the system, which can cause air to leak out of the ducts or other unintended places.
That being said, there are situations where pulling air may be more appropriate, such as when trying to exhaust air from a room that has no external ventilation. In such cases, the inline fan would be installed in a way that pulls the air out of the room and into a duct or other ventilation system.
Ultimately, whether an inline fan is better at pushing or pulling air depends on the specific needs of the ventilation system and the orientation of the fan within that system.