What's fun is equipping the Attack up badges like Power Plus, Jumpman, All or Nothing, P-Up D-Down, etc, etc.
Also, most people like Bobbery the most but Vivian is my favorite partner. Probably because Fiery Jinx is like a cheaper, slightly weaker Bombastic (I think that's Bobbery's last move).
Also, Vivian does a bit less damage with her Shadow Punch but you can hit enemies anywhere on the screen, so it's better imo.
The downside of Vivian is her low HP(yes, I know that this stops being a problem by using badges) and the fact that some enemies are inmune to fire. Also, Spiky Parabuzzies are annoying to defeat. Sure, they have low HP but they are inmune by most of your techniques, ground or not.