I will use Vipin Gupta’s metaphysics to clarify the difference in a simple way.
Mimamsa means personal authority, i.e., authority as one.
Purva Mimamsa means “authority within one” to be the causer of the effect desired. The
effect desired is the action that leads to the desired result.
Uttara Mimamsa means “authority without one” who causes a reaction within the causer
seeking to enjoy the fruit of action given as a result of one’s inaction for the impaction of
everyone’s authority. It forces everyone to be conscious of the “authority with one” and
worship “authority as one”.
Karmaphaladata is “authority with one” to be the giver of the fruit of action given as an
effect of the reaction within the causer after becoming conscious of the cause.
The cause is the potential for one to be the fruit everyone consumes to be conscious of one’s
divinity as potential God once someone decides to make one the medium for realizing
God and becomes the leader of the pack of followers.