[MattLi]

There is another situation which could occur. The robot could not not be the max height and/or width. It could be a square robot.

In anycase a reason to pick a wide robot as opposed to a long robot would be that it's easy to turn. It also takes up more area around the rack so you could block easier.

Reason's for picking a long robot are, it's easier to build a stable long robot than a stable wide robot. You could get into the spaces between bots defending the rack easier, and it can very easily accomidate an arm.