Honestly, your question is too ambiguous to answer. By "best" do you mean most effective in blocking the aromatase enzyme? If so, then the "best", more potent, will also probably have the most side effects. Also, just because one compound is more potent mg for mg does not mean that another option is not as good, since up-ing the dosage usually provides the same effect.
To give you an answer you can actually apply, letrozole has been cited by broscience as controlling both estrogen and prolactin. Most actual studies I have found indicate prolactin levels were pretty much stable but that does not mean that if prolactin is elevated it won't stabilize levels. Letro also induces libido issues for most men. Arimidex is a preferable alternative for most. I personally like formex on-cycle. I think its potency is lower but the sides are lower as well and usually it is sufficient to control elevated estro.