I think that both the Native and Native III have advantages. The S30V Native is thinner than the Native III and has a slicker action. The American made Native is much easier to flick than the Native III. The American made Native is also easier to "Spydie drop." The American Native has the S30V blade, the latest wonder steel. The Native is by far the cheapest knife that you can buy with S30V blade steel. I haven't had to resharpen my Native yet, but it is truly sharp as all get out.
The Native III has a thicker and more contoured handle. If your hands are big, the Native III may be a better fit. The blade of the Native III seems like it should be a better cutter since it appears to have a thinner grind. I know for a fact that VG-10 steel is very easy to sharpen. Many people seem to think that the Native III's wire clip is better than the Native's clip. I really don't know. Check out the Spyderco section of Bladeforums for more information.