From the reading I have done on these models, it sounds like Viewsat has introduced the MaxHD as the more price competitive little brother to the 9000HD. They both have the same processor speed and quantity of on-board memory, and the 9000HD's user interface looks like it has been cloned for the MaxHD. However, the MaxHD lacks the terrestrial tuner that the 9000HD has, so you can't hook up a regular antenna and tune in the over-the-air broadcasts.
I believe I saw something that the MaxHD will support PVR capability, but the software side of that is not fully developed yet. Today, the 9000HD supports PVR use, but they are still working on adding features to it's capabilities.
Recent posts from others are stating that the long term goal is to have the MaxHD be the affordable single tuner HD unit, while they expand the 9000HD to support dual satellite tuners.