The main difference when the Panny 500 and the Sanyo Z2 had their shoot-out was the abiltiy of the Sanyo to be easier to mount from a "non-center" mount. It lense could be manually adjusted, before you had to keystone correct digitally. The next generation Panny, the 700 had worse keystoning ability than the 500.
Now, with that all said I don't know if both models have the same feature set when it comes time to mounting and aligning the unit. But, I can tell you -- it take some time and patience to mount and get the "pitch and roll" and the angles and keystone perfect for your screen. (especially like mine -- which is a home made one.) When I buy my next projector, I will definately look into these features closer.
I love the Panny 500. You will probably not go wrong with either model -- especially when you get to High Def. You will not believe how great a picture these things project.
One more point, you don't need to spend any money on a screen. Wet sanded, perfectly smooth dry wall with a nice flat-white paint is all you need. (I spent months comparing pieces of expensive screen to my wall... very little -- if no difference at all)
Good luck with your projector choice. You're in for a lot of fun.
