I'm not the man to talk to about it, as I dont know an awful lot. There are others who know a lot more than I do.
My internal flash (one on the camera) is very hard to use when tal=king photos, and ends up with shitful photos. The camera takes awesome photos without the flash though. Different housings allow for different attachments to the camera (for example an external flash). This would allow the flash to be completely on the target, and you can change around the angle of which the light is on your target to achieve different photos.
For example, went Scuba diving at Flinders pier last weekend, a bloke had a Canon Powershot G9 that I was chatting too and ended up tagging along with him. He had the Ikelite housing, and took amazing photos.
Mine, in comparison are about 1/100th of the phoots that he has taken, with the exact same camera. He was also relatively new to photography, but obviously has used photoshop etc. But his photos still have a lot more potential than mine do to look good, even with photoshop and editing.
My fear is that by taking the cheaper option at the time as I just wanted to get into the water, if I get more serious about photography it may get to the stage where I would need to upgrade the housing. Much like buying a Seac Sub speargun, then realising its a piece of shit and uppgrading, 200 dollars later.So I guess, if you have the money and youre going to get seirous, make sure you do your research and speak to the people in the know.
So cmon guys who know what theyre talking about (Rhino, Badger etc) let us know the story.