You really can't tell for sure until they are sexually mature. Sometimes the nice, friendly ones stay that way and sometimes they turn into monsters. If you can keep them until they are mature, that would be the best way to decide which one you want to have around. If not, then maybe just pick the sweetest, friendliest one and hope that he stays that way. If he doesn't, you can always make chicken and dumplings, then go out and get another cockerel to raise!!! LOL
Lori

Lori