A little bit like comparing apples and oranges
So true. One is dinner with a show that lasts about 2 hours, the other is a 5 hour party with a special parade, fireworks, meet and greets, and the ability to walk on or have a short wait for lots of rides...and more. And just an overall really cool atmosphere in the MK.
Do you like staying out late? Do you enjoy alot of the rides at the MK? Do you enjoy parades and fireworks (the pirate and princess party fireworks are the BEST EVER!!)? Does dressing up as pirates interest you? If you answered yes to most of these, I'd choose the pirate and princess party.
On the other hand, if MK is not your favorite park, if you do not like parades or firworks, and if you do not like staying out late, then I would choose Hoop Dee Doo.
This really is a tough choice because they are two very different experiences! Both are great for couples without children.
We have seen the Hoop dee Doo twice, and we have been to one pirate and princess party. If I had to make the choice on our next trip between the two, I'd choose pirate and princess hands down.....but ideally I'd do both!
Either way, you will have a great time....they are both wonderful experiences.
And as someone else mentioned, if you think you will be going back to WDW in the future, then do the Pirate party now....Hoop de doo is there year round and you can do that anytime. The pirate party has limited dates, and you never know when they will stop doing them.