My heart will always belong to Grant, and I do personally like Grant's tune more, because I adore bellowing brass and orchestration. That being said, I think based on what we've seen Wise's music slides right in and is admittedly a lot smoother and likely has a wider general appeal. I could throw Wise on and somebody who hasn't played the game wouldn't bat an eye, where as if I threw on Grant's piece, my peers might be a little confused or disinterested.
I would cite the reasons I love Grant as the reasons it's really reminiscent of Banjo Kazooie, the xylophone especially is quite a hallmark of the franchise. Similarities aside, I think Grant's piece also fits, especially if the map has a massive feeling to it which dwarfs our two protagonists. While I think this game is a great opportunity for Grant to blend his traditional Banjo Kazooie style with a more sleek feel, I certainly hope to hear very classic Banjo Kazooie tunes.
It's also important to keep in mind that these songs ARE works in progress, guys.