Advantages: Allows you to use server resources than be limited by your laptop compute capabilities. Log in anywhere, means I don't have to carry my laptop around. As long as I have a browser, I get the same environment to work. Mental peace that my work and data are always safe. I can drop my laptop in a swimming pool and yet I will not even lose the last character I typed on that presentation I was making.
Disadvantages: Yeah, I cannot access my system while on an aeroplane. Can't think of anything else honestly, unless you live in a zone where the internet is as bad as on aeroplanes.
All in all, prefer the browser-based virtual machine any day. The advantages outweigh the single disadvantage of the need for a stable internet connection.