The Transform component stores data only relative to its own parent. This means that accessing and modifying a Transform component's position, rotation, and/or scale properties could potentially result in a lot of unanticipated matrix multiplication calculations to generate the correct Transform representation for the object through its parent Transforms. The deeper the object is in the Hierarchy window, the more calculations are needed to determine the final result.
However, this also means that using localPosition, localRotation, and localScale has a relatively trivial cost associated with it since these are the values stored directly in the given Transform component and they can be retrieved without any additional matrix multiplication. Therefore, these local property values should be used whenever possible.
Unfortunately, changing...