Pat Rice retires around 2014 tho , so i went with Neri . I think for a good assistant you need judging players potential and ability to be high since you need that to see hidden things about players . Also he has to have high motivational skills - for your team talks. He also has to have high tactical knowledge to tell you why your losing 1 - 0 to Bolton. Its not essential for him to have high coaching abilities just mental abilities, unless you really need him to coach aswell.
Pat Rice is really good and he's my first choice on every game, but he's always reluctant to leave Arsenal. So I ususally go for Baldini or Vilanova (spelling :S).