Gattuso is a young player that is growing season by season. His distribution used to be terrible but he's getting better season by season and he's a starter no question, but if we are going to bring in a midfielder for the squad why would we bring in a youngster? He's not going to play that much to develop sufficently (eg. Donati, Dalla Bona) and when he does come in he's not going to replace Gattuso sufficently and how much is this younger player going to cost?
Davids is free, left footed, versatile to play alongside and instead of any midfielder we have, Gattuso will be better for the competition and not be threatened long term knowing Davids is over 30 (Ambrosini can only hope for injury to Pirlo and Gattuso to get a game, they're certainly not going to retire anytime soon) and if people are worried about Davids causing trouble, there are plenty of games next year (CL, Coppa Italia, an extended Serie A) and as I said above he can come in for Pirlo, Seedorf, Pirlo or Kaka (4-4-2). Plenty of chances and we haven't even talked about injuries yet.
Our slip up in this year's CL and those draws that gave Roma hope in the last month were down to fatigue and Ancelotti, when it came down to it, not really having the confidence in Redondo, Brocchi, Serginho etc to play them when we needed our first teamers to rest. That cannot be disputed.
We have a very young midfield. There is no problem adding a class act who is free, versatile and over 30. Who is STILL playing exceptionally.