I like the normal Link sprite. It's very good, looks a bit like TP Link. Very well done.
The Oni Link, however, isn't as good. His arms look very straight - more so than on the normal Link. His eyes are too near the colour of his tunic or hat, so they don't stand out as much, which I don't really like. In general I don't like the colours - they are far too bright and alike.
So if you darken the colours a bit and make them look a bit different from the others, the sprite could look a bit better.