Best Western Golden Spikes. Vs. Holiday Inn Express in Hill City.
Go with the Trip Advisor recommendations for what YOU are looking for. I've heard good and bad about both.
You have to make up your own mind on some things.
Based on reviews, I don't think you can go wrong with either one. I'd look at the amenities and pricing and choose from there. I also like looking at traveler's photos. To me, a comfy bed is of the utmost importance. If one property gets more "comfy bed" comments than another, I'd go with that one. However, I understand it's about what's important to you, not to me. Good luck!