Our team has used a mecanum drive train for the last three years and we've had a lot of fun with them.
As the robot driver for the past two years, I can assure you they're wonderful to control, and driving becomes a lot easier with mecanum.
Controlling the a mecanum-powered robot is a lot like moving a character in a first person shooter video game, which I'd assume many students are familiar with already.
Couple a mecanum drive train with gyroscope technology and now your robot can always move relevant to the driver (No matter the orientation), which in my personal opinion makes controlling the robot even easier.
While a downfall may be that you lose a lot of pushing power, the versatility gained to out-maneuver the defense matches said downfall quite well.