Hi
We've stayed at the Polynesian concierge twice, and the Wilderness Lodge concierge once. We liked them both, but they also are very, very different, with a big difference in rates! (prices).
The Wilderness Lodge's concierge is located on the 7th (top) floor of the resort. From up there you get a wonderful view of that gorgeous lobby. To my DH and myself, the lobby is the best feature of the resort, with proximity to the Magic Kingdom (icluding boat transportation), second.
There is a "new" concierge room on the 7th floor where they place all of the food offerings, plates, drinks, silverware, etc, but the seating is still out along the 7th floor itself. (Previous to this new room being built, the food was placed on tables in the hallway). There are small and large tables with chairs and there are very comfortable leather sofa/chair/coffee table seating groups so you can sit with your food and drink, and look out over the lobby. (There are also some seating groups that face the 2 large flat panel plasma tv sets).
We *really* enjoyed sitting and looking down at the lobby each morning while having our breakfast. Some people see the lack of an actual "lounge" (Separate room with couches, tables, chairs, tv, etc) as a negative, but since we love the lobby so much, we enjoyed every moment we were there
The Polynesian concierge is in a building by itself, the Hawaii building, and only people who are staying there have access to it through their room cards.
One entire end of the building (the end closest to the volcano pool) is the concierge desk area (on the first floor) and the lounge (2nd and 3rd floors). The walls that face out to the lagoon and Magic Kingdom are floor-to-ceiling glass, so you can watch the fireworks and see the castle from the lounge.
The back of the lounge on the 2nd floor is where the floor offerings are set up. This entire building was recently redecorated and it really looks beautiful. There's also a small glass-door fridge that holds cans of soda and boxes of chocolate milk, skim milk, and whole milk that guests can help themselves to. There's a small children's sitting area, including a flat panel plasma tv.
Up on the third floor, there is another flat panel plasma tv and couches, and tables and chairs, and board games that you play. This part of the lounge overlooks the second floor of the lounge, and it also looks straight out to the castle.
I have a lot of pictures of both of these concierge lounges on my web site. Click the link below, then scroll down just a little to see my most recent pictures from the Polynesian concierge, we just got back 2 weeks ago. Right beneath that are the links to the Wilderness Lodge and the Polynesian which are from this past summer.
Enjoy!
P.S. Oh, to answer ypur question "How do they compare?" I'd have to be honest and say that if your finances permit, stay at the Polynesian concierge in a lagoon view room (garden views would be nice too) as your first choice, and the Wilderness Lodge concierge as second choice (much less $$$).
We DID love the Wilderness Lodge, but our opinion is that the Polynesian concierge lagoon view rooms cannot be beat
My best experience has been with AKL with a close runner up of Epcot areas resorts - BWI followed by BC. AKL is leading because the lounge is more spacious and the ability to go on safari! The IPO's for AKL & Epcot resorts are the best hands down IMO. That doesn't mean I didn't enjoy CR this past summer. The ladies on the 14th floor took incredible care of our family while we were visiting despite the oopsies we had. You just can't beat the view we had @ CR either. 
Many of us have our favorites. 
aw: ALK lover here. The bottom line is what theme do you think you would enjoy the most.
