Your gut is right. After a quick search, it seems that the power consumption of a seawater desalination process is less than three kilowatt hours per meter squared for a large-scale plant.

However, the downside of desalination plant will be the cost of the infrastructure and the time it might take to have it up and running. With the "water extraction from air" machine, the cost is lower(I assume) and the size is smaller(Height: 259 cm, Width: 610 cm and Length: 224 cm). Seems like it might be quick to have this MoP up and running faster than the desalination plant while costing a ton of energy in the long run.