There's benefit to using different types of communications with supervisors. As mentioned, methods such as skype/facetime or otherwise calling can be great for idea sharing, discussing multiple things in one session, or having the chance to discuss other matters such as wellbeing etc.
Email or other similar options have the potential to be good for more direct or straightforward questions/single issues, although only if the supervisor replies. It's quite easy for things to slip down an inbox out of sight and get forgotten about, or added to a 'to do' list which then don't get answered.
One of the things I like about scheduled sessions within the moodle environment is when it populate your calendar, and remind you at a certain time that you're due a chat/collaborate/whatever with 'x' person (e.g. supervisor).
Using a mix of communications with supervisors can be useful, although has the potential for the student to feel like maybe they're pestering the supervisor (or for the supervisor to feel pestered!)