I didn't realize until yesterday afternoon that I hadn't actually finished AU - I was only about halfway! I read the Silence chapter and really, really dug it. Wouldn't mind going back there.
Storywise, I like SA/Roshar the most for its (continuing) depth in scale and character arcs. It's most close to WoT, which was my first (long-form) High Fantasy series (LotR's length feels quaint by comparison!). OB felt like a little bit of a firehose with the additional settings/cultures mixing in and the increased insight into the Listener/"Voidbringer" PoVs and expanding Surgebinder abilities.
Magically, I really like the Metallic Arts - especially in the Wax & Wayne era. Less all-powerful Mistborns and more uniqueness in the Twinborns. I liked the slightly shorter and quicker pacing as well. I have a feeling Hemalurgy will come to the fore in later books with more crossover between some of the systems, in potentially dire/sadness-inducing ways. =/