There is an official controller that all robots need to use per the rules. It's (or at least was ~5 years ago when I last competed) a National Instruments cRIO.
I think this decision was made based on NI giving a large cost break on the units.
Supported languages for the cRIO include LabView and Java, making those two the prominent languages that teams use.
C++ was also always supported but from the one year we used that I can guarantee our team's dev speed was much less than LabVIEW. Something about the data-flow UI and live probing of values and VI controls view made it so much more intuitive to develop a robot with. We had a mecanum drive that we developed a dual layer PID system to control individual wheel power using a PID, but also a PID control on wheel rate. The effect was a super smooth but extremely fast control scheme that also had the effect of the robot pushing back if it were moved without user input. Great application in 2014 where the field was entirely open and physical defense was key, but I would have preferred to have normal wheels and all of the traction benefits that come with them that year instead.
