I've never actually used any of those processors so I can't say either way, but here is an idea, you might want to think about using an FPGA demo board and using soft cores, that way you have greater control over how you implement your hardware and can tailor it to your robot over and over again add to it and take away from it. The performance would more than likly go up and like I said with an FPGA you have he ability to add new custom hardware to suite your needs without adding any new physical ICs. Just a thought.