Synchronous vs. Asynchronous

In some ways I preferred synchronous because it seems like it would keep students' attention better. Students would be more likely to goof off during a recording, causing us to possibly re-record, but there's no going back if you're live. Synchronous would work better for demonstrating actual communication in German with a native speaker. For such activities, synchronous could be very helpful.
Overall, asynchronous seems to offer more benefits for German. As a class, we would have the opportunity to replay difficult speech patterns rather than asking someone to repeat themselves. It would also give me the opportunity to make sure that all video that we as a class might send out will be respectful. I would like to use asynchronous video to communicate with a class in Germany. It would be a big step above having a German penpal. Students would prepare video messages to send to their German peers. This would give them a realistic context for communicating in German.