We have cruised on HAL 3 times and have Westerdam booked next Feb.
If I could compare HAL to anyone it would be Princess; smaller pinnacle and vista class ships (the older ones) that have promenade decks on older ships; dark wood and lovely artwork throughout ships, wonderful beds, showers over bath like PCL mini suites (which I don't mind) and fresh flowers everywhere.
Food was always good and crew very much like Princesses.
Saying this, we have cruised on Zaandam, Noordam, Koningsdam and will be on Westerdam in '25.
"I'm looking at a couple of cruises out of Singapore Dec/Jan. I have heard that HAL skews old but that doesn't bother me so much."
Didn't find much difference in passenger demographics from Princess to be honest 😏