I've a few issues with Samsung pay and none really pertain to the service.

First is just usability. I'm a recent Windows Phone convert and enjoy the Microsoft Launcher. Between the launcher's app drawer, the navigation bar, and the Samsung Pay drawer, I'm in drawer hell at the bottom of the screen. Next, I trust Google just a tad more than I do Samsung with my stuff. Lastly, I just loath the cluttered screen that is the Samsung Pay app itself. Android Pay fits more easily into how I use my phone and works at all the places I used my previous phone. But, if I could alieve issue 1, I would consider Samsung for the rewards.