Historically warriors were a class of society with, as Infanteer points out, qualities we wouldn't necessarily consider desirable in a soldier. I think there was an article in the CF Journal a couple of years ago that points this out much better than I can. However, a stab at it:
Historically warriors were:
1. Individualists
2. Self-centered
3. Fighters for the sake of fighting/booty/the "honour" of fighting for its own sake
4. The sort who regarded most other classes of society as inferiors and regarded the killing of inferiors as inconsequential
A recent historical example could be the Japanese in WWII.
The qualities of a soldier, rarely seen in "warriors:"
1. Discipline
2. Group action
3. Regard for soldiering as a profession - with attendant professional development
4. Considers himself an integral part of the society he has chosen to risk his life to protect
And in closing: warrior societies tended to get their collective butts kicked by soldier societies (I.e Romans v. most barbarians - at least before the moral collapse of Roman society; Russians v. Japanese in WWII; British v. <insert tribal group here>) partly because "warriors" disdain technological advances and their application to warfare, while the professional soldier constantly searches for ways to apply new technology to the battlefield.
Acorn