estrogren block

I am pulling my hair out, cannot decide which AI to use. Anastrozole, Letrozole, Exemestane, or Tamoxifen Citrate? (even tho not really an AI) I usually run 20 mg a day of Nolvadex (Tamoxifen Citrate) and usually add in 20 mg a day of Mesterolone about half way through the cycle. But on here I...