Gaara will win in the desert. He has ultimate defense...and can also fly using his sand...then he can attack from the sky...or maybe Sand Tsunami.
But in the Rain village, Gaara will have a great disadvantage. Here A will win.
ideed gaara will win in the desert but not in rain... due to lack of sand but i think maybe if gaara became able to break down buildings into molekyules and then put them together as sand he would prob win...
Gaara anywhere.Water has not shown to be a disadvatange for his sand,but oil,and has a minimum effect.The second mizukage was able to destroy his sand,but never touched Gaara,because he didn't use the same sand to defend himself.