Nowadays, GNOME and Xfce consume about the same amount of resources by default. The only difference is that GNOME makes more serious use of your graphics card.

Nowadays, GNOME and Xfce consume about the same amount of resources by default. The only difference is that GNOME makes more serious use of your graphics card. KDE with lots of effects >> Unity ~= KDE with fewer effects > GNOME ~= Xfce >> LXDE