Nightwing Dick's got better fighter experience in martial arts and acrobatics, he was even able go a couple a rounds with much tougher opponents such as Bane, Lady Shiva, Ra's al Ghul, Deathstroke, and even Batman. Barbara is intelligent but she's not one of the best fighters in the Bat-Family.
Batgirl Batgirl beat Nightwing in the 2011 book they were fighting she was upset he wasn't trying at first then he got mad and she moped the floor with him I saw a couple others were she one but can't remember what they were called I read the Batgirl 2011 book yesterday but she one fair and square
Agreed, with medium or low difficulty.