Try Berettaforum.net, go to the FAQs and look for the thread on the 81 models
Even Wikipedia has a pretty good breakdown of the Beretta 80 Series models and variants: https://en.m.wikipedia.org/wiki/Beretta_Cheetah
Short answer is that I don’t think it should matter for nylon or leather, though maybe when putting a square-trigger model in a hard Kydex holster molded for a round-trigger model.
There are enough of these guns out there that the holster maker should be able to tell you if the holster will accommodate both trigger guard styles.