As pointed out in the previous thread, comparing P10 and 5050 is somewhat apples/oranges--the Sony S75/85/new V1 is more like the 5050--bigger, more control (Aperture/Exposre priorities, full manual), probably a better quality lens (Zeiss v. Sony), etc. But everyone compares, because Sony has chosen to make an inexpensive housing only for the P series, while Olympus makes them for both their lines. Ikelite lists housing for S85 at $900.
That said, why would anyone use the Sony? Familiarity--with Sony camcorders, memory sticks, infolithium batteries, etc. Very small/lightweight--a convenience for travel, etc. Like me, they might own Sea and Sea MMIIEX lenses, and S&S makes (made??) a conversion lens adapter for the Sony, Canon, Minolta compacts, Olympus PT10, but NOT 15. (On the other hand, it seems nearly impossible to get one of those adapters, and I had to search all over the internet and make many phone calls before finding one.)
The question of quality of photos intrigues me. Many (esp. Dee) keep saying Sony is great for above water, but not under--I'd like to see some direct comparisons, or an explanation of why the optics (or electronics?) would be better in one situation than the other. Re green color, my first and only digital experience was in fairly green water (Channel Islands), so the background was definitely green. But external strobe made for good subject colors. I'd attach some pix, if someone would kindly explain (or point to a post) how to reduce the file size.