Pretty similar. Not sure what OMV uses as a FS but Rockstor natively uses btrfs (a FS I used for years and trust) so it was a no brainer for me. Everything else works as expected, nfs, smb, snapshots, backups, etc. The only add on I decided to use on top of Rockstor itself is for Duplicati for B2 backups. I hear a lot of good things about FreeNas too.
That it was mine 😂