Verdict
K2 Plus brings a bigger 350×350×350mm volume and Creality's CFS multi-color system at $799. X1C is smaller but more polished, with Bambu's mature AMS ecosystem at $1,099.
Buy the K2 Plus if: large parts (300mm+) are common, you accept the still-young CFS firmware, want the budget over polish.
Buy the X1C if: mostly mid-size parts, AMS reliability matters, you bill enough that one X1C saves on failure costs vs experimenting on the K2 Plus's newer ecosystem.