This in my opinion goes to Gaara.
Gaara's sand wont be affected by tobirama's water like people seem to belelieve.
Gaara can put of a sand wall to block tobirama's water attacks and while tobirama is focused on knocking down gaara's wall all gaara has to do is create sand under tobirama's feet and drag him under ground. The use sand requiem and gaara wins.
Im sure it would be a difficult match but when the dust settles im pretty sure gaara will win.