I just almost bust a gut laughing at all this "measurbating" between camera choices.......Ha ha ha...........
The Sony RX100 has a bigger sensor and fast AF but not good macro out of the gate without spending more $$$$ for accessories. Sony made a fast focussing bigger sensor camera but the menus and adjustment requirements blow
There's just no other way to say it compared to Canon menus and adjustability.........The Canon G15 has a super fast f1.8 -2.8 lens and yes, smaller 1/1.17 sensor but at lower ISO of 80 - 100 and good exposure delivers great photos.
Doesn't matter if you shoot manual / S-TTL or TTL in an Ikelite hard wired TTL housing (with Ikelite DS strobes) or full manual the Cano G15 will produce nice files to make prints up to 11 X 14.
For online sharing? The file size and such is a no brainer..........
These forums are becoming more gear intensive versus shooting technique. CDHK is another pet peeve.
While RAW file capture can help it won't turn crap into art
Why in the hell would download CDHK to a camera that already DOES RAW files? Simply silly and more measurbating specs and not real world shooting.......
I don't know about you but once I'm underwater I better have a planned subject, proper lens / flash set up in mind or it's a wasted photo dive
Then again these days I don't obsess as much about "getting the shot" as I did back in the film or even early digital days.
It ain't the gear that'll make the difference but using your camera more above and below learning its strengths and weaknesses.
YMMV........
David Haas
www.haasimages.com