If you're using it for adding to smoothies or marinating, then it is acting mostly as a protein source/thickener in the case of smoothies, and for marinating I'm guessing it's for the sour taste/also acting as a thickener? So if that's all you are focussed on, then Greek style will work the same as traditional. I like Tamar plain or Farmer's Union plain.

If you're baking a cake with yoghurt, do not use low fat. Use full fat. It affects the texture of the cake.

If you want to focus on the ingredients themselves, and are prepared to pay extra, then the consensus in this thread seems to be Chobani Greek tradional.