There's nuance between every single F variant. The F77 isn't exactly the same as the original 4704 boards, which aren't exactly the same as the F ATs, which aren't exactly the same as the F XTs. They all have different acoustics due to their cases, which is the biggest difference. F XT is a little more musical than the others because of the sheet metal bottom casing, F AT is a little muted and lower-pitched than the others because the whole case is plastic. The 4704s sound a little between the two in my experience with the chonky zinc cases. I don't have an F122 but I'm sure that's a little different too.
The biggest difference between the reproductions and the originals is they actuate just a tiny bit higher and the springs are a little lighter.
Unless I wasn't sitting down and comparing a repro F77 to my original F107 side by side painstakingly, I wouldn't be able to tell the difference. They're great boards.