[MikeE]

We use command-based because it provides a framework with some degree of abstraction which is also fairly well documented and supported.
Our software team usually consists of 1-2 students plus me, and I'd rather act as a mentor than a programmer. My job is to be a safety net, giving the students a sense of confidence so they can try to solve problems that they may not attempt if the success of the season was solely on their shoulders.
If we were creating much more sophisticated robots then I see the advantages of a bespoke framework, but command-based provides a good sandbox for learning about OO-design, modularity and maintainability.