I Was looking forward to the XZ for some time before release, but when I started looking into the HTC One, my mind was changed.
The on-screen buttons are their permanently even when playing games, which reduces the screen size to that of the One. The call quality is reportedly muffled and also when looking at it in the shop it certainly looks nice, but the quality wasn't as great as I thought it would be.
The One beats it in EVERY aspect apart from being water resistant, I've never EVER dropped a phone in water or had the need to text in the rain so not something I need.
Also the Screen on the One is noticeably superior. I know if you've bought the XZ you'll defend it to the hilt, It is a great phone but the HTC One is just that bit better.