Sometimes, both played. In the beginning, 2010, Higuaín was the first option, but after the injury in his back and the Adebayor arrival, Benzema played more. 2011-12 is the Karim season; GOAT level, really. Gonzalo played well too, but not at that level. More bench player until Di María injury in the beginning of the 2012. In the 2012-13, the same situation, if i remember well. But both played worse. Especially the french.
Last year of his contract. Hasn't renewed yet... Without trade rumors... Very strange.