This will depend on the needs of your workplace. Plumbed eyewash stations are a reliable choice for any emergency within the workplace. Workers can quickly remember where the eyewash station is placed because it stays in one location only. Furthermore, a constant flow of liquid is more guaranteed compared to portable eyewash stations.
On the other hand, portable eyewash stations allow flexibility on the locations where it can be placed. This can allow an easy change of location in case of a hazard change in the workplace. For most workplaces, it is ideal to have both plumbed and portable eyewash stations.