The Difference Between the M9 and 92FS
The main and most obvious difference is the rear sight - the M9 has a post on the rear sight, the 92FS has 2 dots (my preference).
But there are a couple of other differences, as per the photos below...
Around 2003 or so, Beretta changed the frame of the 92/96 to a curved dust cover to strengthen it for the 40 caliber round. And, since the 92 and 96 pistols use the exact same frame. It was just easier to switch it for both.
The M9 kept the same straight dustcover because making changes is a big deal for a military weapon once it has been approved. And, as the M9 is only in 9mm, it didn't really matter.
The curved dustcover frames also have a slight indentation at the top of the backstrap. It brings your trigger finger just ever so slightly closer to the trigger. M9s do not have this backstrap indentation.
I think the straight dustcovers look better, but the curved ones are growing on me visually, and that rear strap indentation really makes a difference for someone with smaller hands.
Be aware that recently, there are a FEW straight dustcovered 92s WITH the indented backstrap (I keep hoping to track one down)
There are also now some new USA made 92s with M9 frames being used. So, those are straight dustcovered frames with no rear indentation. AND, there have been some M9s on store shelves using the curve dustcover frame of the 92FS. So, be aware that there are all sorts of variations showing up in the past year