Our previous CFD predictions of the circular, elliptic, and square jet mixing tanks were re-analyzed to investigate the highest performance jet mixing tank design and the appropriate mixing performance criterion. So, the mixing performance indicated by overall mixing time and maximum mixing time criteria of these jet mixing tanks was compared. These CFD predictions were carefully developed by using our previous reliable jet mixing tank CFD model. For model validation, reasonable agreement between the predicted mixing times and measurements was observed. The results revealed that circular and non-circular jet flow phenomena were significantly different in the near field jet regions. Further, the elliptic jet mixing tank provided the highest mixing performance because of its highest entrainment and turbulence kinetic energy near the jet boundary. Finally, it can be concluded that the maximum mixing time criterion is a suitable mixing performance indicator.