Feature-wise they are a bit different, like rmk has support for Bluetooth and wireless split configurations. But is also lacking some things like display support. The reasons I went with it were for native vial support, easy configuration for the rp2040, and stupid easy pin and keymap setup. I had never written firmware for a new board before this and had a working build in not even an hour after reading the docs.
I don’t plan on running a group buy, but I do have a few extras. PM me and maybe we can work something out.