The Hitachi Twin motor window units are as efficient as a split and probably better at cooling if they are able to cool like the specs say.
However window units require a big hole to be cut in your wall or by sealing up a window. Installation cost is usually a bit higher if you have to repaint or restructure your windows (even though the quoted installation is lower, this assumes the masonry etc is already done).
A window unit is usually more comfortable (IMO) than a split because of the fact that there is always fresh air in the room. It is usually less efficient because of this as well.
Pick your poison, both have their own compromises.