An interesting thing would be to look at the NodeJS issue tracker. I opened an issue in io.js and NodeJS at the same day - the io issue got several responses, was discussed between collaborators, a pull request was made and it is discussed in the next TC meeting for inclusion in the next version.
The NodeJS issue got exactly zero response.
It looks (at least from the outside) that io.js is a maintained project and NodeJS is not.
io.js resembles node prior to 0.11 stalling out for over two years... Responsive community and core contributors. The inclusiveness seems to be much better than it has been under Joyent.
Short of the Node Foundation turning over operations to the io.js TC, I don't see Node remaining the choice platform within the next two years as they diverge farther than they have. I wouldn't mind seeing them re-join, and re-release io.js 1.x as "node" 1.x proper.
It's bad enough that we have to use transpilers (6to5/traceur, etc) for new feature support in the browser... having to use them on the server was a pain... co/koa and similar have been around for over two years waiting for 0.12 to come out of beta... Even then, they were significantly behind v8 and libuv.
If Node Foundation brings io.js back into the fold, great.. if not, I'm with io.js on this one.
The NodeJS issue got exactly zero response.
It looks (at least from the outside) that io.js is a maintained project and NodeJS is not.