To be honest for me personally right now to have a working GooglePlay plugin is the most advantage. But I think this should be ported to C2 as well, since I bought C2 with the argument GooglePlay would work...
Besides that all new features will only come to C3, never to C2. But right now nothing of the new stuff is something I need or want.
The new runtime will hopefully be a huge difference, if that will be good, I will move over to C3.
Right now the biggest difference is a newly designed editor and support to run in browser and different platforms. Nothing I want, but really requested by others.