How Mitochondria differs from Prokaryotes(probably regarding energy production)?
If you mean "why do we have mitochondria instead of our cells doing the work themselves"
Then I can think of several answers.

First, oxidative phosphorylation must take place within an organelle, and requires specialized cellular machinery to occur.

So either a prokaryote can wait a couple million years to evolve these structures, or it can ask its friend to do it, and HE is specially evolved to do just that.

Like the way you hire a plumber when your toilet gets clogged, instead of going to plumber school yourself.

Also, oxidative phosphorylation has to do with oxygen.

Oxygen, when busted apart, can form unstable molecules called free radicals that are essentially bleach.

These molecules zoom around smashing up anything they touch including DNA.

So the host cell says "better you than me!" 
Remember how I said you need an organelle for oxidative phosphorylation?

This is why. So all the "bleach" gets contained.

Two very good reasons why we evolved to rely on a separate organism instead of just making our own breathing organelle.