We tend to judge our resort hotels by their pools and slides, at WDW as well as other destinations. I'll just tell you about the pools and slides at the places we've stayed.
Poly -- the pool is fun. There is a beach entry, a view of Cinderella's castle, and Hawaiian music that you can only hear when you are underwater. There are also bubbly jets and a big waterfall. The slide is partly enclosed, and supposed to be a lava tube running through the volcano. Although it's not the longest, it's definitely not just for little kids and it's really, really fun!
GF -- the pool is similar to the one at the Poly, with a beach entry, a large waterfall, and a slide that curves through the rocks and by the waterfall. My DD thinks that the slides at GF and Poly are similar in length, turns, and speed. The one at the GF is not enclosed at all, though.
AKL -- the pool is really, really large. Beach entry, beautiful foliage and theming (best on property). There is one slide and it does curve. It's fun, but not very fast or steep. I liked it, DD thought it a bit tame. She's 12. It would depend on the ages/tastes of your party. Because of the theming and size, though, we really like this pool. You can also use the play area at Kidani if you stay at AKL. It's the best kiddie water play area at WDW, with "spitting" snakes, tipping buckets, and a couple of slides (still not that big).
BC/YC -- the largest, most creative pool at WDW, with the tallest, fastest slide. Definitely the "best", it's partly enclosed, partly open, with a long straight part then a curvy ending. You climb up an old sunken ship, then slide down the broken mast -- very cool. The pool has so much to offer, with a whirlpool, a sandy bottomed play area, and a river section with a current to float around in. There's also a little kiddie slide for those too small or afraid to go down the big slide.
I can't tell you about the other deluxes or the moderates since we haven't stayed there.
Hope this helps.