I don’t think there is any particular reason for choosing the one over the other. Some aspects to consider:
- Some solvers only provide relative displacements, some only provide absolute displacements. We try to support both, wherever possible.
- Our tutorials have historically evolved mostly based on what each student project needed, and not as a predefined “curriculum”. Reasons are often historical.
I guess that there may be numerical reasons that make the relative displacements better in some scenarios. But I have no idea what the literature has to say in this regard.