Don't forget that pretty much every part of your's and a whales body has nerves in it to detect pain & contract muscles. More body mass means more nerves that

Don't forget that pretty much every part of your's and a whales body has nerves in it to detect pain & contract muscles. More body mass means more nerves that need to send and receive information from the central nervous system. So even assuming a constant amount nerve endings in cm^3 of flesh between whales and humans a whale will have significantly more.