There is not much to separate five-time Ballon d'Or winners Messi and Ronaldo, who are regarded as two of the greatest players of all time.

Both are all-time leading goalscorers for Barca and Madrid respectively, having guided their teams to Spanish and European honours.

Buffon weighed into the debate ahead of his encounter with Messi as Italy and Argentina go head-to-head in an international friendly in Manchester on Saturday (AEDT).

"They are two completely different players," Buffon said. "Messi is more complete, because he starts deeper, has more technical quality and a vision of the game that is worthy more of a trequartista than a finisher.

"Cristiano Ronaldo, perhaps because he is a little older, has become a killer in the penalty area. Compared to how he was before, Ronaldo preserves his energy more, so he no longer goes out to the flank for a nutmeg or trick-shot, but with one ball into the box he can create a goal."

Messi tops the LaLiga goalscoring charts with 25 for Barca this season, three ahead of Ronaldo.