Both of these plushes are from GK World. As you can tell, they're a bit of a Jekyll/Hyde situation. Sonic is pretty well done, with defined and solid construction. The likeness is good, except for the ears wich are a bit pointy and thin. He also has the BDG (Big Dumb Grin) that was over-used during Sonic Adventure 1, and then played-down later. His hands are in different poses, and each of his details seems to be nice and 3D.
Then we come to their terrible Tails. This thing is on Mutant Gear! You can read more about it there...