I have an NVR5x-I series, the '-EI' is current generation.
Certainly the 5 series is nicer than the 4 series.
Naming convention: e.g. NVR
5416-16P-EI
5 = Series 5
4 = Number of HDDs
16 = Number of channels
-16P = 16 local POE ports
-E/I = (Something about AI functions...? or type in the series? I don't know how to word that)
It is a nice NVR.
the main feature is having the NVR processes different AI function on the NVR, rather than requiring the camera to do this processing.
Such as; facial recognition and line crossing.
There is limits,
Usually facial recognition by NVR processing is limited to 2 channels and IVS (line cross, cross region) by NVR processing is limited to 4 channels.
These limits do not exist if your camera supports the AI function.
Why do I think it is good:
It means non-Dahua cameras can have line cross detection or facial recognition.
Is it worth the money?
I don't know your exact circumstances.
I bought my NVR for very cheap, about the same cost as two 6TB HDDs.
It seems they sell for ~$1,200USD. That is a lot of money for not many features that a VMS and well built PC can give you.
If an 'all-in-one' solution is what you're after then it may be worth it.