Re:_ Hamatora is a continuation of Hamatora. For whatever reason the creators decided to use a different name for the second season, which confuses tracking sites like Trakt.tv. Anyhow, by whatever name, it's basically the second half of the same show. Still exploring a world with mutants...excuse me, "Minimum Holders"...through a few powerful characters, with a goodly amount of social commentary on the lives of the powered among a mostly non-powered populace.
Not much change as far as the production values go, as you'd expect from a continuation. One thing they did add which I wasn't particularly fond of was a different transition method between scenes. Rather than just fading to black or a short blank transition, Re:_ Hamatora uses a transition that freezes the final scene image, does some funky coloring, then morphs to the next scene. It's not a major thing, but I found it distracting.
I found the major conflict in Re:_ Hamatora much more interesting than in Hamatora. The Hamatora villain felt contrived, with no real purpose behind his motivations. Insanity was the only motivation that made any sense to me. The motivations of the Re:_ Hamatora antagonist, on the other hand, were much more clear and believable. I thought they did a much better job explaining his actions (and those of his various associates), though it did take a while...not until the final episode, in some cases.
I'd only recommend Hamatora/Re:_ Hamatora if you know already that you like the genre. If the idea of powered individuals impacting the world aren't your thing, I doubt this will change your mind. The show is a well-executed instance of that genre, though, and I enjoyed it.