Alias is the basic 2004 model. The ram is a little better designed (from a wear and tear standpont), the bolts a wee bit lighter, the boards are a little better, the grip frame is moved forward a touch, the front asa has a larger air gallery, and the LPR is shorter. The build qaulity seems a little better to me, too, but others might disagree.
The biggest diff for me is the better balance that comes with moving the grip frame forward. They basically are just a bit nocer in a lot of little ways than the pre2004 models. All those are basically the same mechanically, although the Z series or GZ lacks an LCD screen. It is sort of the "speed" of the bunch- slightly more basic.