Remember that feeling when you unlock a new weapon, whether it's a Devil Arm or gun and you excitedly look into the upgrade menu to see the new list of skills and the Swordmaster or Gunslinger extra abilities?
It feels nice to unlock new actions and abilities as you go along throughout the game.
Even if Nero only has one gun and one sword, you still get the feeling of unlocking new things, like getting Snatch in mission 2, Devil Trigger in mission 6, Hold in mission 8 and so on.
You just don't get that feeling with Vergil.
I had millions of leftover Red Orbs by the time I got the DLC and I immediately unlocked all his abilities by Mission 1.
I'd like Vergil to get his own story campaign where he gains or discovers new abilities.