The Virtual Forbidden City is, of course, limited in scope; there’s no comparison to Second Life here.However, it has several advantages to using SL.
Accessible on any computer - I have downloaded it to my Acer Aspire One netbook, which would not cope with a full blown virtual world such as Second Life or Twinity.
Rich content: this is unusual for virtual worlds, which are great for truly immersive learning and for social interaction, but have little text, audio or video content of their own
Easy to use: the learning curve with the Virtual Forbidden City is pretty shallow, in part because the avatars are not able to do what would be possible in SL (build, use voice, fly, etc) - that said, there are some activities to do within the 3D environment