Had to make this decision last fall.
Pro G1X: bigger sensor, slightly better IQ.
Contra: heavy. To less difference carrying a dslr.
Pro RX100: small, fast at the wide end.
Contra RX100: no hot shoe. No switchable viewfinder. No filters atachable (yes, but....)
To make the story short: I wanted a much smaller camera compared to my big toys, something I stick in my pocket and forget.
I took 9200 shots since last october, and I love it. I take it almost everywhere.
Big plus: people are much relaxed when you use this toy.