Sarah taught Kirsten how to use an RSS sync application (netnewswire). Kirsten taught Sarah how to mount remote systems over ssh for use with her local OS and how to transfer large or small amounts of data from her local machine to a remote cluster (sshfs, fuse globus online).
From a cursory inspection we can determine that neither recorded video nor live tutoring have the edge in modern pedagogy. While recorded lessons can be delivered to an asynchronous audience and offer the lecturer the chance to deliver his lesson with polish and planning, they are no longer able to adapt the pace or content of discussion to the students in front of them and are forced to adopt a single, potentially limiting approach. And while the live tutor can absolutely tailor their lesson to the individual students, they must be charismatic and empathetic enough to read their students, brave enough to teach on the fly, and able to avoid losing the thread all together particularly in tangential discussions. They may also find that it is difficult to schedule interactive sessions, and that high throughput teaching is completely out of the question.
The question of which approach is better has, of course, been addressed by more focused minds than ours. What we can offer is that there is no one right answer, and that students and teachers both should seek out and capitalize on the approaches that they have found to work for them. Sarah and Kirsten both would prefer to teach and be taught in an interactive session. If the same content were only offered as a pre recorded lesson, we would both greatly appreciate a well annotated lesson that offers plenty of additional resources in the case of pedagogical mismatch.
To answer the question of how to tell which technique was more effective, we can only fall back on the old canard of pre test, during test, post test.