I would rather go with the S1 because the future of the mount is more certain, but I would wait until the second generation arrives. At the moment, Nikon Z6 is also one I would consider because the lens mount is so different that it will be better into the future than the others.
The E-M1x would be useful, but I would prefer to go with the Panasonic G9, if I'm sticking with micro Four-Thirds.