Spain has tied with Italy with longest unbeaten streak of 37 matches.
Argentina has been most successfull footballing nation in past 8 years.
Though the averages possesion of both teams are close, Spain is collectively better than Argentina in most stats so far with exception of the goals Argentina scored. They have most goals scored in the tournament.
Man to man, Spain is better as well with exception of Messi who out performs everyone.
Spain has only conceded one goal and it was a cross from the right - something Messi was doing against England.
Messi playing from both foots and across the field could be very challenging.
Martinez is big issue as well. He had only 54% save percentage this tournament - a major reason why Argentina conceded so many goals.
In short, Spain outclasses Argentina in most aspects but the different once again comes up due to Messi.