The two Spanish sides are in action midweek in their respective first leg semi-final encounters with Barca facing Chelsea and Los Blancos in action against Bayern Munich.
With the mouth-watering double only days away, Wenger was keen to give his opinion on the two ties on his blog for Yahoo! Eurosport.
"On the pitch, Real Madrid have an advantage [against Bayern] due to their technical and physical strength," the Frenchman said.
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"For me, it's 60-40 in favour for Madrid. Since the start of the Champions League [this season], Real Madrid have been more stable than other sides and the most impressive in the competition.
Commenting on the other semi-final between the Blaugrana and Blues, Wenger stated: "Barcelona are favourites, it's 65-35 [in favour of the Catalans] but players like [Didier] Drogba, [Frank] Lampard and [John] Terry have extensive experience in this competition so it may not be so easy for Barcelona."
Wenger also predicted an all Primera Division clash in the final of the Europa League and was particularly complimentary of Athletic Bilbao, who face Sporting Lisbon in their last four tie.
"They have been the revelation of the season thanks to their positive philosophy on the game. What surprises me is that they have won only 10 league games this season," he added.
However, despite rating the Basque side, he was keen to state that he believes the winner of the other semi-final between Atletico Madrid and Valencia should be considered favourites to win the competition.
"One of these teams [Atletico and Valencia] will win the Europa League. Both teams are very close though so it's impossible to choose a winner," he concluded.