It looks the same only with the minor feature.
Flex 5250:: Appliances is container-based architecture and it's immutable storage capabilities (Any data inside immutable storage cannot be altered and deleted)
These features provides additional security layer against ransomware/malware.
Appliance 5250: Only built-in intrusion and detection system (The appliance intrusion detection system (IDS) consists of a custom Symantec
Data Center Security (SDCS) policy that runs automatically at startup.) and WAN optimizer.
Note:
Starting with software version 3.1, SMBv1 protocol has been disabled and
replaced with SMBv2 protocol. SMBv1 protocol is vulnerable to ransomware
attacks such as WannaCry and Petya, and is no longer considered as secure.
SMBv2 is now the minimum supported protocol for NetBackup appliances.
