I have compared both and liked the CX better on all pieces (DAC, transport, amp) that I compared them on. More immediate, better microdynamics, lack of shouty upper midrange that helix series seem to have. The Python Helix will give you slightly more bass slam.
I also have extensively compared both the Black Mamba CX and Black Mamba HC CX to the Python CX and the Python CX murders either of them, much to my dismay. I'd say the HC is maybe 70% of the Python and the non-HC is 50%?