http://basketballprospectus.com/article.php?articleid=496 Great breakdown and comparison of Nelson, Rondo and Harris.
Depends on what you need imo. Rondo and Harris are both amazingly fast, Rondo is more of a traditional pass first PG with great defensive skills. Harris is more of a slashing guard who can get assists by commanding a double team.
Did they really need to do a statistical study to show this? It's pretty obvious. Derrick Rose might take it away from Harris soon, maybe not. But Harris is clearly on a different level than anyone else, and Rondo/Nelson don't really show the potential to reach his level.