I have been looking into that for the past couple weeks. I called x-10 and they told me that both software packages are virtually the same. Any modules, etc that would work for ActiveHome also work with HomeDirector. They also use the same computer interface, so you can buy the HomeDirector kit cheaper and download the ActiveHome software to run it with.
The HomeDirector kit is on special right now for $9.89, at Worth Dist, better hurry because the sale is being held over, check it out!! [Link: worthdist.com]

Craig