I'm using the UX31A. The 1080p IPS screen is amazing compared to a regular 1366x768. Zenbook UX31A is capped at 4gb because it's soldered on to conserve space. The UX32 with the regular spinny hard drive is upgradable in both HDD and RAM. If I were to do it again I'd get the UX32 1080IPS with Nvidia card which gives you the best of both worlds:
ASUS Zenbook UX32VD-DH71 Intel Core i7 3517U 6G 500G 24G SSD GT620M 13.3IN Widi Windows 8 Ultrabook