Anyone who votes for Killer Frost is a heathen.
At least Captain Cold actually requires work to do well with him, both in low and high levels of play. This is mainly because his moveset sucks and he's situational. But that in a way makes him more exciting to play and watch.
Killer Frost is just a Frost from MK knock-off, sliding around everywhere and doing Up+3.
Not to mention, Captain Cold actually has a redeeming side to him. Did you see his arcade ending? Or the fact that he refuses to kill/harm people when he would do a heist? Killer Frost is just a whiny baby constantly saying that men need to be punished and bs like that.
The type of people who say Killer Frost is cool, are probably the type of people who claim she's their waifu. They probably have a very dirty body pillow of her on their bed. They probably stink and smell very bad. They probably also suck at playing Injustice.
Killer Frost sucks. Case closed.