Pirlo is more like a much more creative Xabi Alonso...more direct and long pass oriented than Xavi. While they both can play the key pass, Xavi is much more the glue that ties the team together, where Pirlo is looking to get the ball forward. Xavi is also better at maintaining possession. Pirlo sometimes takes on players much faster than he is and loses the ball. Xavi rarely makes that kind of mistake. Xavi is better under pressure.
I like all playmaking midfielders- Modric, Pizarro, Sneijder, to name a few others.