To each his own.
The size and weight differences are meaningless underwater or in traveling, IMHO. They are both small cameras. Yes, you can slip the RX100 in your pocket, but other than that in real world diving I can't see a difference. In fact a slightly larger footprint is more stable and controls are easier to access. If you add the dome port, it is the same weight or less than a large wet mount dome like the Inon or UWL lenses.
As noted, the Panasonic has direct controls, and much better layout than the Sony. You have to reprogram the Sony, maybe using up another control to get to something as simple as ISO. I know you like the RX100 series, but I think this is a better camera, notably for close focus and video. That's my opinion from shooting both, you're welcome to yours.