Here is a pretty good comparison of the RX10 and new Panasonic FZ1000 (3 pages long):http://www.dpreview.com/previews/panasonic-lumix-dmc-fz1000/6
A comment says it appears they use the same sensor.
Note that in the photo comparisons jpegs are used. A comment embedded in that section says that when shooting raw they are much the same and much better, as expected.
I didn't see anything mentioned about the slow zooming of the RX10 and whether the FZ1000 has the same very annoying characteristic, but there is this comment about the FX1000:Performance is blazing fast, for both autofocus and overall operation.
Probably that means that the zoom control also is much faster.
The Sony has a 24-200mm f2.8 lens and the Panasonic has a 25-400mm f2.8-4 lens. There wasn't anything that said what the Panasonic's aperture is at 200mm. Probably around f3.5.
Anyway, as usual, they each have their stronger and weaker points.