Tough one, if your other half likes Benidorm then Majorca may be the better option. I've been to both islands 3 times and overall I prefer Ibiza just for the fact that it's smaller and easier to cover the distances if you're wanting to travel about plus you're never too far from the airport which means faster transfer time to resort. But Majorca is lovely too. Both islands have their big and lively resorts. Looks like you'll have to toss a coin. BTW, Alcudia is a huge sprawling resort. I stayed there 20 years ago and it was lovely, went back 3 years ago on a day trip from a nearby resort and hated it. It felt like Blackpool but with better weather.

palma nova is lovely lots to do but quieter than magaluf which is within walking distance if you want a bit livelier one night the hawai mallorca apts are top of the hill and have great views get a sea view we stayed in the hawai hotel next door and the views are brill 5 min walk and your in the centre of it all , lovely beaches great walk along the front
we are going to ibiza this year es cana fancy a nice relaxing holiday this time it's lovely to ,have a good one wherever you choose

If you could put up some personal preferences, group makeup etc., then suggesting a suitable island would be much easier. We have been to Majorca many times covering most of the tourist hot spots. All have different qualities, some quiet, some more anglicised etc., Likewise certain parts of Ibiza are fantastic whereas others are clubbers havens.

Put your list up and i'll try to add some more info

try ibiza for a change.