I’ve used both. Octoprint with Marlin and CNC.js with grbl.
CNC.js is great. I love it. I’m not sure if any of the features are missing for Marlin, but it’s much more focused on CNC. It has work offsets, understands the gcode is for cutting, not just travel moves. It has a great visualization. Yeah, try it out, let us know how you like it. It was really the reason I switched to grbl, so maybe it’s time for me to switch back.