Season mode is actually quite good. It can feel a bit short, once you've finished. But overall, still worth playing and enjoyable. There's tons of different stories, if you lose a certain match, or having made a different choice here and there. And yes, you do get to keep the title, as well as defending it whenever a new challenge comes along. Same for choosing what type of match you want to have, whether it be a ladder, tables, a regular single match, etc.
There also comes a point where, if you're playing someone from Smackdown, and you win the World Heavyweight Championship, you'll eventually be drafted to Raw, and the title will be taken away from you. Only to replaced with the WWE Championship, and you start defending it.