If you are just loading for pistol, and never intend to move up to rifle, you can get away with the Dillon Square Deal. It's fairly cheap, but it's downside is it's small, harder to convert.
The Lee progressive has a following, and they are very cheap. Many people look down their nose at them, and never having had one, I can't offer an informed opinion.
The Dillon 550 is a better built press than the SD or the Lee, but it doesn't auto advance. It can handle rifle cases, and it has the added flexability of interchangeable tool heads, so once your dies are set, you get to leave them alone.
The Hornady Projector is built more solidly than the Dillon 550 or 650, and is ideal for rifle and pistol. However, it does not offer interchangeable tool heads, and it's origional powder system wasn't as good as the Dillons in progressive use. Many of these failings have been corrected in the newer Lock and Load press, and there is some backwards compatibility. One design feature that I personally liked was that the shellplate advanced on both the up and down stroke, smoothing out the transition and causing less shaking of the powder out of the case.
The Dillon 650 has the advantage of the quick switch capability of the 550, and the addition of an automatic case feeder.
The Dillon 1050 is the ne plus ultra of reloading, as it does every operation on the downstroke, it feed automaticly, and it can also swage the primer pockets of military brass.