If you want passive 3D projection, then a dual projector is the way to go.
Polarisation modulators are only interesting if you have an expensive DLP theater projector and don't wan to spend tens of thousands on an equivalent projector.
For the home, a dual projector setup will provide significantly better quality for less money.
At the moment there are two different passive systems which are popular.
Polarised : it's the traditional way, but it requires a silverscreen...