Asynchronous discussions are able to be more informative and deliberate. Synchronous discussions are more suited to one-on-one or enhanced with a video. I had a professor once set up a video chat at the beginning of the semester to answer any questions students had for real-time feedback. A few things he did to get around some of the downsides to synchronous chats were to have students send email questions ahead of time that he could address on the chat, he recorded the chat and made it available to everyone, and he scheduled a second chat on a different day of the week and a different time of day.
