I bought the original version of 3:10 to Yuma because I wanted to compare it with the Russell Crowe remake. I liked both. Crowe played a great bad guy, but Glenn Ford, normally cast as a good guy, appeared to enjoy playing a rogue. (3:10 to Yuma is now my favorite Glenn Ford movie.)
I won't discuss specifics, but there were several plot or character improvements in the new version, however, I preferred the ending in the 1957 film. In fact, the contrast in endings tells a lot about Hollywood’s reluctance to embrace traditional heroes. (Elmore Leonard's short story has yet another ending.)
Production values were certainly better in the later version. It's also fun to watch the two trailers back-to-back to see how selling movies has advanced in the last fifty years.
If you're a film student, movie enthusiast, or just like Westerns, both versions are great additions to a private library.