Beretta 92FS and M9 are two types of handguns from the same manufacturer i.e., Beretta. Although both look very identical, however, there are some differences between the two, especially in terms of specification. When you check the specifications of the two handguns, you will realize that they share a lot of things in common.
However, while M9 uses a blue synthetic grip as its finish, Beretta 92FS uses a black synthetic grip and a black Brunton as its finish. Also, M9 has some features that cannot be found on 92FS. For instance, there is an inscription on the barrel of M9 written together with a certain serial number.
Another difference can be easily noticed in the various existing models of the two handguns. While M9 does not really have other models, 92FS has another model known as 92FS INOX. According to history, Beretta 92FS seems to be the older creation of the two.