Pooling equilbrium refinement
There are many refinements of pooling equilibria. For starters, you want to make sure all your equilibria are Perfect Bayesian Equilibria. After that, you can also require any equilibrium to survive the intuitive criterion or other forms of forward induction. Lastly, you could also require things like efficiency or symmetry. 

The choice of refinements is not always straight-forward, it depends on what you mean by "best" and how well the assumptions implied by each refinement match the story of in your model.