The tiny scissors mentioned are also expensive little devils. I use the kind of scissors most elementary school children buy for school and I use a seam ripper if I have to take out stitches. I think it's more precise.
The main attribute for embroidery scissors is, in my opinion, sharpness. They have to be sharp, so they can cut through various thicknesses of thread.
I'd love to have a pair of vintage embroidery scissors. They are usually ornate and lovely, but I don't have that kind of cash when I can get a decent pair for $3.