The selection of a call for Morse traffic can be a "tricky business".
There are several "schools of thought" in this; ranging from being "short", here the "machine-gun burst" of contester special call SE5E stands out, or to having a balanced composition between short and long elements.
I am the second holder of my call, as in the "old days" calls were re-issued if the holder let them lapse.
If someone let the call lapse, usually by not paying the annual fee, it became available to others after a period of one year. In practice, the period became somewhat longer. Calls held by SK:s could be re-issued after three years.
This caused un-wanted consequences, as some did not like their issued calls, and went to great lengths to change them. There also was a considerable waiting-list for two-letter suffixes.
After dealing with a particularly obnoxious call-sign change case in the mid-80s, the regulator lost patience and announced that from now on any issued call-signs would be final and not subject to appeal.
A non-payer would be assigned a new call if coming back. No old call-signs were re-issued after this.
In 2004 the call-sign issuing system was changed with SM being the prefix of the calls previously issued by the regulator. No new SM calls can be issued.
The SA prefix calls are those issued in the new regime by the national society after much easier exams.
Should an SM old-timer that have let his old call lapse want to take up amateur radio again, the old call can become re-issued if it is not taken by someone else before 2004, otherwise an SA call is issued. No SA calls may re-issued, and there are no two-letter suffix personal SA calls. Then we have the cases of "special" or "vanity" calls which are a different subject.
Back to the question of call-sign information content.
My own major interest in 1970 was VHF weak-signal work, and after examining the energy content in Morse characters, it was realised that long signal elements have more energy and are more easily decoded in white noise. This is incidentally the idea behind the TMO signal reporting system used in early EME.
So, when AOM surfaced as a choice, it sounded like a good alternative. The prefix, SM4 in my then case, was not subject of choice.
The call-sign does also have a reasonably nice rhythm and is quite easily recognised.