When a barbarian reaches 11th level they gain greater rage which increases the bonus that they would get when raging.
The spell rage
Each affected creature gains a +2 morale bonus to Strength and Constitution, a +1 morale bonus on Will saves, and a -2 penalty to AC. The effect is otherwise identical with a barbarian’s rage except that the subjects aren’t fatigued at the end of the rage.
Since the spell states that the effect is otherwise identical to the effects of rage, does that mean if a 11th+ barbarian has rage cast on them they instead apply the benefits of greater rage instead of the listed lower benefits which are lower than the ability rage?
Best Answer
No.
It seems like the question in your title and the question in your description are two different things, so I'll address them separately.
Does Greater Rage stack with rage?
No. A barbarian's Rage ability (and, by extension, Greater Rage) and the rage spell both provide morale bonuses.
Can a barbarian with Greater Rage who receives a rage spell apply the benefits of Greater Rage instead?
No. Since this is not specified, it isn't allowed. For comparison, a skald's Inspired Rage ability specifies exactly this-- if your Greater Rage-capable barbarian comes under the effects of a skald's Inspired Rage, you can apply your Greater Rage bonuses instead.