They’se pros and cons to both in-suite and communal.
For the developer, in-suite means more and larger plumbing stacks and more hot and cold water lines, not just the washers and dryers plus hard flooring, curbs and a floor drain if they’re doing them right. You also need to vent the dryers to avoid humidity issues.
For the user, there is convenience in having them insuite as there’s no need to traipse down the hall (it’s also quieter for your neighbours). If your have higher quality quieter machines you can do laundry whenever you want/need without the concern of shared equipment/others handling your laundry. On the other hand, the machines in common laundry rooms are typically heavier duty and capable of doing larger loads in less time. Most laundry rooms also include a laundry sink which can also be quite useful at times.
In suite will also require annual inspections for lint buildup in the vent lines to avoid fire hazard.
Which is preferable probably depends on hope many units are on each floor. In suite isn’t that much more expensive if there are only 6 and not 26 and it’s probably easier to share if there are only 6 and not 26.