There are a few things that factor into this:
1.) The X1 userbase has a higher proportion of shooter fans since it is more of a dudebro console and heavily advertised as such. The PS4 userbase is not as shooter centric.
2.) Last month, you could get Destiny with an X1 for free. Heck, you could get two games with an X1 for free!!
Overall, it's not surprising. In fact, I expected the X1 version of Destiny to do much better than this because that deal had incredible value.