Sony seems more pocketable though. Sensor wise, BSI doesn't have that much of an effect at those sensor sizes, so it's a toss up as to ISO performance. Looking at their current mirrorless APS-C offerings, current gen of Samsung sensor quality is much better than before, but still arguably less good as Sony.
(Note : Samsung applies more heavy handed NR [much much more on the high ISOs] on the RAW [yes, on the RAW] so anyone thinking of comparing the NEX vs NX on dpreview please keep this in mind...)
Honourable Mentions (AKA already released product so no more mystical halo...) :
Oly XZ-1 (Similar sensor size to Samsung, slightly less bright wide open and slightly brighter at max tele)
Nokia 808 (Somewhere inbetween, but sensor size is closer to Sony, double the MP though... And is a prime. F2.4 is also smaller than the RX100 wide open. Pureview tech can help it close the MP gap though, especially in the 5MP or less mode, with 7 pixels forming one pixel, reducing the bayer 'fuzz')
Canon S100 (Similar sensor size to Oly and Sammy, less bright wide open vs either)
To be honest I'm leaning towards the 808 mostly because of the convergence (no need to carry 2 items, a PnS and a HP), and if critical quality is required no one is going to take out a PnS anyway!