Arduino Over VEX

What is better for making a robot with, a VEX kit or Arduino (electrically/programing speaking not mechanical)? What advantages does Arduino have over VEX?

What is better for making a robot with, a VEX kit or Arduino

Depends what the robot is supposed to do. And which Arduino and/or VEX kit (whatever that is) you are talking about. Also depends on which you have and are comfortable using.

What advantages does Arduino have over VEX?

There is an active forum supporting it.