Naruto wins mid difficulty. Sand coffins can be escaped via summoning or clone explosions. Toad oil disables sand. FRS busts ultinate defense. Naruto can casually react to Gaara's sneak sand attacks.
I don't think he even needs clones, Big Ball Rasenshuriken, or summons.
If he doesn't use Sage Mode, he could probably beat Gaara with just Rasenshuriken and the clones required to make it. He was exhausted the whole war and probably has higher base physical abilities.