Agree with much of what's been said above. If the A4's emphasis was size, the C4's is compatibility and flexibility. Once 'minimum absolute volume' has been set aside as a guiding principle, another 0.3 liters doesn't change the equation. It's an ~11 liter case either way.
I do wonder whether the C4 can stand out in terms of industrial design. The A4 caught lightning in bottle in this regard, partially because of its unique size but largely due to its single-piece wraparound front and top. Similarly, the very first iteration of the C4 had a 'je ne sais quoi' about its appearance for many forum readers. It's unclear whether this was due to its dimensions, its boxy edges, or the extruded front, but whatever it was that design seemed to click with many.
I fear this iteration of the C4 has no such defining visual characteristic. It doesn't need one to be a very good case, but I do think this is required of a great case. If you squint the C4 reads like an M1, only with rounded rather than tapered front edges. And the M1 is not a beautiful case IMO.