After completing my class 2, I did both. I did 7 modules for ADR in both packages and tankers and also did ALLMI HIAB with hook, brick grab, clam shell and remote.
HIAB was a complete waste of time for me. Mainly because most of the employers either wanted something other than ALLMI or wanted you to do their own training anyway.
ADR has been more useful in the respect that a few contracts I have had required ADR occasionally and were not really looking for people with experience, just the ticket to make the job legal.
Most HIAB employers are looking for experience whereas ADR they just want the legal requirement to have the certification.
At least that has been my experience in the year or so I have had my license. I certainly won’t be renewing my HIAB when it expires, but I will keep my ADR current.