Use one off the shelf.
The target are Robotics Engineering Students, though of course it will be open to Electrical and Mechanical Engineers who are concentrating in robotics.
I've noticed that many of the RBE students (it IS a brand new major so most are freshmen) have slim to none experience with microcontrollers- even many of the EEs are as well unless they're juniors, and the MEs are hopelessly lost when it comes to this.
While I think the EEs and RBEs could manage having to take a chip, set up a programmer and then set it up in a bread board, I think the MEs and other majors would be turned off by the prospect.
My goal is out of the box ready to run and program.
If I had to order the parts for the kit today I would go with Arduino because I know it can run an H bridge and read sensors and out of the box will work. On top of that someone with little experience can figure it out with little effort.
I will be posting another question in the mechanical section after this one about the robot chassis.