Everything is in data sheets on dahua site..
-I line is EOL and is replaced by -EI line..
Main difference: 2x decoding capability (64 MP/s vs 32 MP/s) for displaying/analyzing video and AcuPick function (which works only with newest 5xxx-S3 WizMind-S cams). But also there are some restrictions in -EI: lower AI capability (2-4x lower channel count for local AI processing, missing Video Meta Data local AI processing). Dahua migrated 5xxx line from WizMind to WizSense line (so lower AI line), for WizMind functions You need go to 6xx line..
If You have 5xxx-I and You fit inside NVR limits there is no need to upgrade.. Especially You have fresh firmware for it from 230928 on dahua website..