I'll kick things off John, I'm sure others will have something to add.
There are only two models of Star reloaders that you are likely to encounter, the Progressive and the Universal. The Progressive is for 38 Special and .357 Magnum only, and the Universal can be set up to load all common pistol calibers, and even .223. The easiest way to distinguish one from the other is the presence of absence of shell locator straps. (see pictures below). Universals have them, Progressives do not.
If you want to load all three calibers (9MM. 38 Special and 45 ACP) on one machine, you will need a Universal, plus dies and shell plate for each caliber, plus primer parts for large and small primers. You can take it a step further by having extra tool heads for each caliber. That way you won't have to reset the dies each time you change calibers, just install the appropriate primer parts and change shell plate and tool heads. One step further would be a small primer machine and large primer machine.
Don't dismiss the Progressive. They are typically less expensive than a Universal, and a very worthwhile investment if you load a lot of 38 Special.
As for choosing a machine, once you have decided what you want, it all comes down to condition.
Bruce