they are more or less the same age, if that is your worry.
Let's not forget, however, that Xavi happens to be playing in the best team in Europe, now, while Pirlo over the past 3 years of his career was part of a team that was full of players who did't have motivation anymore and hurt by management mistakes that failed to strengthen that team and keep it at the top of European football, where it was till 2007.
In short, put Xavi in the Milan after 2007 and Pirlo in this Barca and then we can talk comparison, which leads me to my previous point - it is useless and very unwise to compare players like you guys are attempting to