I don't have hinges problem with the 1S, so I can't tell.
Few things I notice from my 1A:
All shoulder and elbow are not at tight as the 1S, I do not mean joins loose anyhow, it has right amount of fiction which make you less worry about the shoulder hinge, also making posing a bit easier.
Canopy coating is slighty different, this time it is more on the purple side, coating on my 1S looks more like Oakley's emerald and has more reflection.
No crooked skull, the 1S I got has crooked 1 or 2 degree one of the tail fin, actually I didn't notice it until member point it out.