Key difference between the ADM268xE and ADM258xE

Q 

What’s the key difference between the ADM268xE and ADM258xE?

A 

The key difference is the isolation rating.  The ADM268xE is a 5kVrms rating
per UL1577,   
whereas the ADM258xE is a 2.5kVrms per UL1577 rating.