Gaara has shown to be able to move a massive Susano'o (Madara's) To leave an opening for Naruto. He could EASILY use this advantage to make an opening to attack Sasuke, as Gaara's sand has an infinite number of possibilities, he can remove the Susano'o and take out Sasuke at the exact same time. If the fight were to happen, Gaara would of won easily.
Gaara would have pulled Sasuke out that Susanoo and strangled him with his sand
Lol, that's sounds so ease and i could also say Sasuke uses Chidori and kills Garra since Garra's Sand weakens is Sasuke's Chidori.