The CySmart CY5677 supports BLE v4.2, and the CY5670 supports BLE v4.1, but otherwise they look identical. You might even be able to update one with software to get an implementation that mimics the other, but don't quote me on that 🙂
I've been using a v4.1 CySmart USB dongle for my development on the PRoC 022001-00 BLE chip, and I haven't run into any issues so far.
You are probably fine using either one; Pick the BLE 4.2 if you know for sure that you are using BLE v4.2 features to ensure it will be tested for that though 🙂
