There are two areas where I the web version is really lacking compared to the desktop client. First, I do not see an Audio Only mode on the web client. This is nice when you just want to use less resources (computer and bandwidth). Second, the desktop client window is so bulky. Could the video be available in a child, stretchable pop-up window. That way you can use whatever size you like and have more flexibility about putting it in a corner of the screen. The current website implementation has one center window or full screen. It's really not as flexible as the desktop client.
Additionally, I think the desktop client video quality looks better than the web client, but I'm not positive about this aspect.