Here’s a brief analysis of their presidential portraits.

François Hollande poster, is quite close to the people.
A green landscape with a village in a hill, a midday light, and little clouds. Which convey an impression of local, down to earth feeling.
Furthermore, François Hollande is looking at us, like he is listening to us.The dialogue is open. The clear sky highlights his face and his hazel eyes.
The informations occupies the lower part of the poster. The font is quite round and bold which confirms the proximity with the elector.
At the contrary, Nicolas Sarkozy is in front of a calm sea, a cloudless sky. Furthermore the sky gradation give the impression that the dawn is coming. The sea is a strong symbol. Here, it tells that we have to see beyond our boundaries. Or in the contrary to protect our borders. (I can ironically easily imagine a boat people drift in the poster.)
Nicolas Sarkozy is looking to the right, like is having a vision of the future. And he seems quite confident to brave it. (Follow the leader leader leader follow the leader clap clap). The informations are arranged like a movie poster. Nicolas Sarkozy is like a hollywood star.
Ding ding ding !!! Who’s gonna win the match ?!
The answer in ten minutes ;)