As the NX100 shares exactly the same sensor as the NX10, it also offers all the advantages that a large APS-C DSLR sensor offers, namely better performance at higher ISOs than the smaller Micro Four Thirds format. I’d be happy to regularly shoot with any setting from 100-800, and even 1600 is handy at a push. The fastest settings of 3200 and 6400 are less useful though and not quite on a par with the high ISO results from the Sony NEX series.
If you want a mirrorless interchangeable lens digital camera and high ISO quality photos the NEX is the better choice. Otherwise the NX100 seems like a great choice especially since it’ll only run you US$599.99 with a 20-50mm kit lens.