Good thread.
I've just checked mine and I've got one of all three. Placing them together feet to feet, the wide stance RL and FL match pretty well, but the narrow stance FL is almost a full foot width narrower than the wide stance versions. The paint on the RL is almost silver as well, whilst the others are still quite gold.
Other than the stance, the main difference between the FLs are the panel on his back, by his shoulders. The wide stance has 5 clear blocks, whilst the sculpt on the narrow stance seems to be less defined. You can still see 5 blocks, but they just don't seem so clear, although it could just be play wear maybe. The rivet looks smaller on the narrow version, there is a definite gap to the circle on his torso, whilst the wide stance version river fills the hole completely. Maybe the rivets are the same size and the sculpted hole is different size, but the wide stance rivet looks bigger to me. To be honest, the whole torso sculpt looks much more clearly defined on the wide stance version but my narrow stance one has a lot more play wear.
Chris