Redox equations are balanced either by ion-electron method or by oxidation number method. Both methods lead to the correct form of the balanced equation. The ion electron method has two advantages. So some chemists prefer to use the ion-electron method for redox  reactions carried out in dilute aqueous solutions, where free ions have more or less independent existence. 
The oxidation state method for redox reactions is mostly used for solid chemicals or for reactions in concentrated acid media.