I like Nadal a lot. I respect Roger, Novak and Andy but out of the four, definitely my support goes to Rafa. Still, while Rafa says a lot of wise things and is generally very fair, this time I do have to disagree with him.
It is good that we have different surfaces. We have slams on outdoor hard, clay and grass. To me indoor tennis is another surface altogether as it presents entirely different conditions for the players. We are never going to have an Indoor Slam as it would be pretty much impossible to create a site that could accomodate an event as big as a Grand Slam with all the courts indoors. The logistics of an Indoor Slam simply make it impossible. But indoor tennis is a very important measure of a player's abilities just as hard, clay and grass are. And it is right that there should be a very big event indoors where the players can show who is the best on that surface. As there isn't ever going to be a Slam indoors, having the YEC indoors is the next best thing.
The one thing I would add to that though, as obvious as it should be, is that with the YEC being indoors it doesn't reflect who is the best player in the world, it should reflect who the best indoor player in the world is, just as RG reflects who is the best clay court player and Wimbledon reflects who is the best grass court player. But there is nothing wrong with having a tournament at the end of the year which tells us who is currently the best player in the world indoors.