How can a Scrum Master facilitate the most appropriate decision (timeboxed) which is based on consensus, within a context in which two Senior Developers, based on data acquired during the sprint, are arguing over the pros and cons of their solution that they put forward.
What is the best way of facilitating such a discussion so that the best solution can be realised at the
Let's put the idea of "senior developer" to one side, since there is no such role or title in Scrum. The role is Development Team and its members are simply developers.
What are these two developers doing, given their strengths and experiences, to engage and inform the rest of the team so all are franchised in reaching a team decision? That's the skill which needs to be drawn out here. It's the collaboration which ought to be facilitated, not the decision. Whatever choice is made, it is only the right one if it is owned by the team and permits their future inspection and adaptation.