Need purchase advice please

TLDR: Cant decide between: Centauri Carbon Qidi Q2 Creality K2 /K2 pro

Engineering student -> should support higher grade material Multicolor would be nice too Would like to avoid bambu

Hello, I currently have a neptune 4 pro and would like to upgrade. Ideally i want multicolor and support for higher grade materials, but the reviews to each of the previous listed machines are mixed in a way. I dont want to go for a toolchanger yet. Also i would like to avoid bambu. Do you have advice which of these machines would be best suited for my needs and which to avoid? Thank you very much