5E is a major release by the largest RPG publisher, and will be a force in the industry no matter how good or bad it is.
Nemenera is a minor publication by a famous name.
but more on what the games might be. 5E looking like 1E with more robust characters creation, at the moment, and Numenera looks like it is going pell mell down the path of having classes.
I know this might be the wrong thing to say, but in some way, I feel that D&D is the only system that can still get away with having rigid classes and be of any interest to me.
Now a good open build system would be very interesting to me.
As for the story behind Numenera, it just does not hold water for me.
I think it will be a good game, but I have to go with 5E as more interesting.