What makes it your favorite?
Practicality: absolutely fantastic transportation, the best of the monorail resorts imo. Multiple ways to get home from the most annoying park to leave. Being able to catch the Epcot monorail direct with a 5 minute walk is insanely cool and imo more than offsets the much longer and more impractical walk it has to MK compared to GF and CR (and it's not even possible atm because of construction). I have always had excellent bus service there too, which isn't something I can say for other resorts. Commuting to MK in the morning for rope drop is so unbelievably pleasant because Kona Island is right there before the monorail station, so you can grab your coffee or w/e and just go. Say you're too tired to go into MK for the evening, being able to just grab a dole whip from Pineapple Lanai, watch the show, and walk back to your room after watching fireworks from the beach is so incredible. Basically everything that makes the Poly so fun to visit is even better when you're a guest there, even 'Ohana is easier to get into when you do thanks to a policy change a couple years back. But you also have easy access to a ton of great dining and shopping right next door at GF, and Steakhouse 71/Cali Grill is a short monorail ride away.
Oasis patios are a steal for what you get especially now that you get snacks and beverages with them. The Oasis pool in general is actually my favorite on property, even more than the feature pools pretty much anywhere except maybe GF.
The subjective: god tier immersive theming. the Poly really gives you that "I'm on vacation!" feeling as soon as you arrive. A beautiful view of the castle. The entrance is stunning, the lobby smell so lovely. I love the history of the place as a Disney geek...there's not much of the old school Vacation Kingdom of the World vibe left anymore around WDW, but the Poly's got it in spades. There's an "It" factor to the resort that I've not felt anywhere else. Yes, it can get bustling at busy times, but it's also very peaceful most other times. An odd but pleasing mix of kinetic energy and tranquility. Boutiki is the best resort gift shop on property imo. Some of my favorite resort food anywhere at these restaurants (my favorite breakfast is the Loco Moco at Kona Cafe, and if you ask they will still make it for you with real meat instead of the soylent green listed on the menu). The Oasis pool bar is better than most QS at other resorts.The blend of retro and modern decor and design. The Moana rooms are my favorite on property, though that's on the cash side. Lovely, lovely CMs.
Cons: the price, obviously, is the biggest one. I badly miss the Twilight Feast. The Lava Pool is people soup most of the time (we tend to do the Grandpa Simpson meme whenever we forget this and attempt it). They keep chipping away at what makes it special. But these are minor issues in the scheme of things imo.
I'll put it this way, I spent my 40th at the GF, and absolutely do not regret it because I had an absolutely magical trip despite it being the peak of pandemic weird Disney. GF became my other favorite resort, a very close second. But if it had been an option, I'd have spent it at the Poly in a heartbeat. (Instead, I just got my favorite meatballs from Capt. Cook's.)