Been on both ships in the last year, similar in size and the ships are quite new, but the crowd will usually be younger on HAL.
The entertainment on HAL suits our needs better, the main stage is disappointing but the music walk has Rock and roll, a bit loud but 60's through 80's. BB King which to me is more Motown than blues and a piano bar with 2 player who complement rather than duel. The music in these venues has been really top notch and I think they are putting money here instead of the stage.
Princess had more traditional stage shows and that's where we spent our time on the Sky. The venue musicians were hit and miss and were usually just a guy or gal on a guitar or piano. We did have a steel drum team on one of the Sky cruises that was quite good and played music that we know.
So the crowd on HAL will be older than even your oldest, think 68 avg age and there is probably little to keep a 4 yrs old happy, but to us the venues are great.
On Princess more likely to be similar in age to the older passengers but still skewing a bit older.
We're 65 and like older music so HAL is our first choice but we go on both as well as Celebrity.