The POLY and WL are our favorite resorts to stay at and both have pros and cons. What we find as a pro might be a con for you; as you will fiind everyone on these boards have fantastic and expert advise on both resorts, good and bad. It might be helpfull if you tell us who is going...a family of little ones compared to a couple will have different pros and cons.
It is just my husband and I who usually go; I also take my 80 year old mother too. There are so many different aspects when I choose a resort. Is the trip your first time at the parks?
Will you be spending more time at the MK or EPCOT, HS,AK? Transportation will be important. The pros of the POLY are the ease of transportation in regard to the monorail. We feel that hands down the monorail is by far the quickest way to get to the MK and the TTC ( where you can take the monorail to EPCOT). You will need to take a bus at both resorts to go to HS and the AK. The bus system at both resorts have been a hit and miss with us. The boat transportation to the MK at bothe resorts has been the same...sometimes you have to wait a while and others the boat is waiting for you.
The theme of the resorts are sooo different! The POLY is very lush and tropical and the WL has a north western feel to it. The Pros of the POLY are many! We love the decor of the rooms, main buildings and the tropical landscape. The POLY beach is an excellent way to watch the fireworks at night and the water parade.... not to mention a great view of the castle. You will not be able to see the fireworks & castle from the WL beach.
There are pools at both resorts and they can get crowded! We love the quiet pool at the POLY; the volcano pool is usually VERY crowded for us to relax in. The quiet pool at the WL is part of the WL Villas and is much smaller.
The main pool at the WL is nice, but does not have the volcano and the great slide for kids at the POLY. There is a slide in the main pool at the WL and a seperate kiddie pool. Ther is no hot tub at the POLy, which is such a shame. The WL has 3 hot tubs...2 at the main pool and one at the villa pool.
The rooms are so different at each resort too. The POLY rooms are much bigger than the WL. The rooms are in multiple outer buildings at the POLY compared to being under one room at the WL. There are balconies or patios in all the rooms at the WL, where the POLY some of the 2nd floor buildings not not have balconies. The noise level can be high at the WL if you are in a lobby room. I think these are some of the woods view, standard and honeymoon suite rooms. The POLY was quieter even though we were in a first floor room facing the lagoon of the Tonga building. There was alot of foot traffic...especially at night when people were going to and from the luau.
The restaurants are simply not compareable. The POLY has far more choices in sit down restaurants and better counter service. O'hana and Konas at the POLY were fantastic...Whispering Canyon Cafe and Artist Point at the WL were ok. The counter service at the POLY, Captain Cooks had much more to offer and didn't seem as crowded as Roarking Forks at the WL. The Tampu Lounge at the POLY has some great drinks

! Territory Lounge at the WL has your standard bar cocktails/beers. The pool bars were very similar to us. The main thing about the POLY in regards to food, is that you can simply hop on the monorail with ease and go to the Grand Floridian and the Contemporary for other sit down restaurants and counter service. At the WL you will need to take the boat over to the Contemporary and then take the monorail. For us...its to much of a hassel.
I have to mention the price difference between the two...the POLY is more expensive. Location, Location, Location!!! You simply can't beat the location of the POLY. The WL is much cheaper and one of the cheapest Deluxe resorts on site. We like to stay at the deluxe resorts but unless we get a fantastic rate, we usually stay at the WL.
Not sure if you are looking to stay on the club level or not. We have stayed at both and at other Deluxe resorts. I believe they have the best IPO and CLs. They are very differnt and you do get what you pay for in the cost. Having stayed in the standard and honeymoon suites at both, there are pros and cons with each. If so let me know...I will add those also
Hope this wan't too long and that it helped somewhat.
Have a fantastic trip!!