There are other bonuses, but the Free Champion is the most beneficial. Daemons recieve a bonus to their summoning roll if their in favoured sizes, meaning they'll reach combat sooner. Read the rules for each Cult army for more information on what favoured units do for you.HeXsim said:Are there any other rules to this or is this only one?
Now, whether you keep your Plaguebearers favoured or not is up to you - Do you want the chance that they are summoned earlier? Or do you want to have the larger pack size?