Coldcard has Source viewable firmware with reproducible builds - Certainty around the firmware. Rasberry pi has closed source firmware, backdoors could theoretically exist without you knowing.

Coldcard Firmware updates are also somewhat dummy proofed as the Coldcard does a PGP key verification automatically.

Coldcard has Lots of little advanced security features that are nice to have but probably not a big deal unless you have a large stack.

Seedsigner you either have to trust an assembler to be honest or build and load yourself.

Respect to Seedsigner though, great option to have in the ecosystem if you’re tight on funds and willing to assemble yourself.