I have not cruised on P & O. My cruising experience so far has been, in order of preference, kinda, Celebrity, HAL, RCI, Princess, Carnival and MSC. I have never had a bad cruise, all are good but some cruise lines do some things a bit better than others and IMO is where they gain their followers.
On my last HAL cruise, in one music trivia, I could not answer any of the questions - they were all too modern, about 80s and 90s artists.
If you're looking for fun activities Carnival would cover that. Rock climbing, flow riders, water slides skating, dodgem cars. HAL and Celebrity have none of that and, unless they had music venues during the day are fairly staid. I'm not into art shows or auctions or dancing which seem to have lost their appeal although many cruisers long for some music and ballroom dancing (which was never my thing). I recall either Celebrity or RCI having silent disco which is fun to do and watch.
MSC have dance classes but we're not seeing them in Oz atm but I think they are coming.
HAL usually has a veterans meet. On my last HAL cruise this was well attended, so much so that at the request of participants another two were scheduled - I attended them all. Participants came fom US, Oz, NZ and UK and IIRC included one or two still serving attendees.