I completely agree. People often focus on resolution, but a nice scan needs good dynamic range, I would chose something that performs well in terms of dynamic range.
The 4K one that’s been in use in the commercial scanners since 2019 is the IMX253 (2nd gen), but the Pregius S would be the best choice now the 4K one is IMX535 and you can do realtime scanning with USB3. I don’t know if Flir has a camera with that sensor though, Emergent does and you can configure their cameras with USB3 connections if that’s what you want, and also Dual ADC which means you can do HDR scanning like a Scanstation but without needing to double-flash. The next one up from that is the IMX530 which has 5.3K resolution, but the resolution is a bit high for realtime raw capture over USB3. The budget version of the 530 is the IMX540, I’m not exactly sure how much that will affect scanning performance, but I’ll bet it still gives good bang for the buck.
If you don’t need 4K just look into the lower resolution versions they perform quite well.