The 'nice quality' streak of the earlier smaller plushes stops with this Sonic. The doll to the left is 'small' the doll to the right is 'medium'...though they're from the same set/run, as you see the embroidery on the eyes and the fabric is all alike.
Unfortunately the smaller one has a sort of bizzarre mis-shapen head with huge mouth and over-done eye ridge. The seam-lining on the head also gives it a lumpy quality that isn't helped the the "horn-ish" ears. The Amy did not suffer from these, so why should Sonic? This Sonic can also have a missing buckle. (It should be glued on, but some are not...so do observe first) Info by Chibiko.

With the "medium" doll, you can see they're using a scaled up pattern (the head is still too flattened-oval shape) from the previous one, but sheer size helps fix it. This one's shoes aren't as puffy, the buckle looks a little more in-place and his arms are a bit more proportionate. The head looks less 'alien' and more pleasent, despite the fact that it appears they did NOT scale up his eye embroidery. Also note that the mouth-size is the same as the small doll, only here it looks better because the whole face is bigger. A curious development for the series.