I don't think Garrett is overrated. He's been playing injured all season and still producing. He can dominate both the run and pass and will get better as time goes on (provided there's no long term injury concerns). Might only see flashes in his first season, but I think like Clowney, when it clicks - look out.
Having said that I'm also a fan of Barnett, and don't think a team could miss by picking either him or Garrett.
My fear though is that we're going to take a QB. I'm not overly thrilled about the QB class this year (looks much stronger next year) and would rather we built up our defense and strengthened our O-Line before throwing a rookie QB into the hot seat where he's more likely to fail without adequate support around him.