If you look at how Spain and France played in their last match, It doesn't seem too difficult to guess who will have more control of the game in the semifinals. As we know, France was quite overwhelmed when facing Portugal and I think they were lucky enough to be able to force the match to a penalty shootout. If only Portugal could maximize every opportunity they had, then France could have lost that match.
You are right but what we should also consider is that this season Euro is nothing compared to other seasons because if you watch this league matches you will see that all there performances are not that good, though I no that Spain performance on the previous seasons was quite good but we cannot be sure of that performance this season and besides in terms of performance France has shown more force than Spain but we cannot also be certain of there success on that match.
However one of the things we should also consider is the players involved on that match, though the both sides has a good players but we cannot dispute the fact that France has a lot of good players but however if Spain managed to win the match that means the trophy belongs to them because I have not seen any club that would challenge them in terms of performance.