NZXT has chosen well by looking at their success of the H-Series of enclosures and trying to improve on it. The original already offers excellent build quality, a unique and useful design and tooling options, and a good feature set for a small enclosure like the H200i. With the H210i, you get that same great chassis with a few improvements. It now ships with the V2 of NZXT's smart device, USB Type-C, and an updated SSD tray to show it off through the clear glass window.
All these are a bit subtle when it comes to refreshes, but considering the original was already a great case and still is, there is only so much that can be done. That said, I would have loved to see RGB-equipped fans, for example, to make the most of the smart device V2, especially considering the street price of the original H200i hovers at around US$100 as opposed to US$120 for the H210i. The USB Type-C addition is certainly nice as well, but it would have been even better with two full-size USB 3.0 ports as the wiring is there and the only thing that is missing is the plug. These two elements—the fans and the I/O—would have made the refresh stand apart more from the previous version while offering more bang for your buck.
That said, the H210i is still adequately priced considering the unwavering pursuit of both design and engineering. Everything from the material mix, intricate tooling, unique audio port + adapter, monoblock case connector, and even the purple USB 3.0 port means you get NZXT's uncompromising vision of an ITX case.