I've had experience with both, owning a Prizm II and having a family member recently purchase a Prizm for "business purposes."
Not to spoil your fun, but you probably won't see a massive difference in the two projectors. From far away, at least if you sit in a dark room, the Prizm II is definitely brighter and gives more detail in the darker parts of an image. If you are close to where the image is projected, the physical "pixels" look smaller on the Prizm II, but this is not immediately noticeable.
However, I think the 'izm II is very much a better projector. Reading small text is easier with higher resolutions, and (this might just be my experience) the Prizm II seems more color-accurate.
For presentations and the occasional video (classroom, meetings) the Prizm II is much better. Plus, its darker color blends in more easily with desks and tables.