CX has lower hdmi bandwidth of 40gbps vs 48gbps for C9. This basically means it can't do 12 bit 4k60 without chroma subsampling which the C9 can. Also it doesn't have any form of DTS decoding.
Other than these issues, it is a good tv. It has lower posterization issues compared to C9 in HDR modes and also has slightly better luminosity. Overall a good tv but firmware right now has a few bugs and needs updates.