As a puppeteer (a person who works with many kinds of stuffing and padding every day) I can say that if the movement of the arm is important, then the materials are very important.
Different kinds of foam, batting, polyfil, cotton, would all bunch differently, all glide past each other differently, all allow for different sorts of freedom of movement.
I'll often start a piece and realize "Oh, that's going to bunch up weird with foam, I'd better use fill" In fact, beneath seemingly simple padded objects, there is often fairly complex engineering.
I'm not talking about metal and gears. I'm talking about soft materials put together in just the right ways to allow for the right movement.
For instance, to make very thick padded arms on a costume commission last year, I created 1.5" polyfoam ribs held together by fabric, then on top of that a layer of quilted batting, and patches of very slippery fabric in certain places to avoid catching on the underside of the fur. There would have been a million ways to padd out a non-moving figure to look like this, but most of them would have looked pretty terrible when they started to move.
All this is to say, the failure of one padded suit to allow proper movement means about as much as the failure of someone who has never baked to make a decent souffle by throwing all the ingredients together.
