There is a thread on this from about a week ago but anyways........
IT IS MORE THAN JUST THE RAIL!!
The A1 has a built in recoil buffer, which makes it the only choice in my opinion, unless you are going for the Stainless/Inox.
The 92fs for years was haunted by the earlier productions cracking locking blocks. This was a problem that likely was more talk then actual occurences, but nevertheless Beretta felt it necessary to address the issue with the new 92A1.
Another nice thing about the A1 is the removable front sight which can be swapped out and upgraded, unlike the FS which has the front sight cast into the frame.
I chose the A1 for the above reasons, the rail, and the overall fit and finish just seemed nicer to me.
I was gonna go with the INOX, but stainless drives me crazy with all the marks, and dirt that shows up on the finish. LOL
Here is a video:
[YOUTUBE]nUjbgp8hT_k[/YOUTUBE]
And a pic of the recoil buffer: