RX100 to replace old Panasonic GF1?

I have a GF1 with 20mm pancake lens with I use as a secondary camera besides my 5D MII. However, I still think that the GF1 is too big to put in my pocket, so I find myself hardly using it really. At first I was thinking about getting the S100 (or the successor). However, I went to the sony store yesterday and the RX100 is really small enough to fit into my pocket. I was thinking of getting the RX100 to replace my GF1. My only concern is the image quality. Since the GF1 has a larger sensor, my I going to expect much worse quality images on RX100 in low light?