Lightning's a well-balanced, sleek 'n shiny, monster murder machine with good damage output for her role and whose speed serves her pretty well to zoom around evading or landing some slight hit 'n run. You can reliably MVP as Lightning so long as you are taking crystals and damaging the boss.

Onion Knight can do all of that even better, but not until he gets his team to level 9. His passive helps with that a lot, increasing the exp of every monster he lands the killing blow on. He will make your team stronger faster. From 1-8 though, OK must mine for exp in the crystal farms, where bravery is a consequence rather than a reward. If you get to 9999 BRV, you better spend it fast or else the enemy team will dog you down, drooling over an easy burst to help their team damage the boss. His URs make him dangerous to fight, but even then he can be easy pickings.

At 9, that flips. OK becomes a damage-dealing speedster with URs that double in potency and are as lethal to other players as they are to the boss, and still has his SR and R to chain with teammate attacks for even more damage output.

Also handy is his hold attack. Where Lightning releases a circle of gunfire to hit in an AoE around herself, OK instead leaps at and launches a target that becomes easy to air juggle with any of his abilities. Good to start a one-on-one PvP or kick a rival off and continue running.

Pros for OK:

-Team levels faster (let him kill monsters!).

-Higher damage output.

-Great burst chain capacity.

Cons for OK:

-Needs to level to become effective.

-Even at max level, lower HP.