I'm trying to remember, wasn't Leon a sorcerer before he became a spawn? Or am I getting that mixed up?
As for him being the best, maybe he had more skill than the others from his time alive. That wouldn't be surprising if he still had sorcerous powers. Or maybe the others had been tortured for so long that they just didn't care anymore about the special room privilege. Maybe Cazador simply lied to them and said Leon was "spawn of the month" to generate jealousy and competition for fun.
