Main difference between old 5442/5842 and those new version with -s3 suffix is a new SOC.
SOC is a chipset with CPU/GPU/ISP/NPU (all processors) in one chip..
Old version was construction from 2019 and had underpowered SOC.
New version is from 2023 and have much better SOC with 2 generations more modern ISP (image signal processor) and much powerful CPU/GPU/NPU.
Old version is obsolete from 2023.. No new features and no guaranty of new firmware releases..
New version have a much better image quality (especially at night) and a lot of not used computing power - so Dahua after one year on market added many new features (animal detection, long distance mode, AcuPick 2.0 with human look attributes etc)...