Hey, depends the situation, Gaara normal is very good as skillbroken, the shields are real plus he gets all the stuff like kaze one, but if you are fighting someone that can steal or stop your barrier then he's not in the best place. i really like both and i would choose depend on situation always.

That's a great question

Really depends on the situation:

For example one factor would be if your enemy uses auto-barrier and is faster than you, then you would rather use Normal Gaara.

2nd important factor, if you are using it in GNW/Bond then you would rather want Kazekage Gaara because normal Gaara barrier buffs only your team and not your teammates.

Overall I would say:

Normal Gaara better if you are weaker/slower, Kazekage if you are using some damage/nuke teams and confident with having the auto-barrier.

I'd say Kazekage is better, he is a lot easier to 5 star when you hit level 95 since you can get 25 of his frags and have him as an elite mission.

However Normal Gaara does a lot more damage on his mystery.

Really up to you what you need.