You bring up a good point about penguins. They and chickens are both birds, so why are we finally eating chickens but not penguins? Cuteness definitely plays a role.
You won't even see a penguin until you reach high latitudes and they eat fish...
Even if they both tasted good (which I have no idea) very obvious practical reasons would explain the difference.
My argument is about starting up a baby penguin slaughterhouse in the north pole right now and how much activist resistance you will get versus a crocodile meat slaughter house in Florida.
The adults get too muscular from all the torpedoing through the water.