Contemporary garden wing. It's the least kid-filled of the three (I love kids, but groups of them running around aren't always conducive to romance), and the resort has a grown-up, almost sophisticated feel. Staying in the garden wing is nice as it's much quieter and calmer than the rest of CR, yet only a very short walk away. The CR rooms are very nice (nicer than the BLT rooms look in pictures, although I've never seen the latter in person).
CR has better dining available than Poly, and better views of MK. My experience of the Poly was that it was nice, but also crowded and busy-feeling, more so than at any other Disney resort I've stayed. So many people gush about the Poly's theming, but having been to Hawaii in real life, the Disney version is a bit underwhelming. The Poly volcano pool was people soup, as well (this was even after the gate was put up).
CR's pool is less flashy, but that also means fewer pool crashers. It also has cabanas available to rent. It's so stress-free to be able to walk to and from MK at all hours of operation, without having to worry about the monorail being down or missing the boat launch.