Well it all depends on your camera experience and level of knowledge. I am the moderator for the Canon HF-S10/S100 channel on Vimeo. And have been doing camera research for the last two months before making the purchase of the Canon HF-S10. I can give you a few things to keep in mind.
If weight and size are a big concern for you, then yes you should be sticking to a consumer camera, such as the XR520V or the HF-S10. Now if you intend to shoot footage topside, for vacations, family outings, etc. You may just want to go with the Canon HF-S10. In auto mode, the Sony does have better low light capability, but at some cost. There has been notable noise levels with the Sony at low light. This is mainly due to no manual control for the gain. The Canon has manual control for gain, which in the right hands can match the Sony's low light capability without the noise level. It may seem like I am pushing the Canon, but I am simply pointing out the points that pushed me towards the Canon.
Another thing I should point out, is the Canon has a 24Mb/s bitrate, which I think the Sony is either 16Mb/s or 19 Mb/s (not 100% sure). The whole problem with HDD or flash based camera's in the past was the bitrate. HDV was 24MB/s, well Canon has solved that problem. One issue with both of these camera's is they are avchd which requires some major computing power to edit and render, versus the HDV format.
I feel the Canon has the slight edge. The reason for my opinion, in daylight Canon is the clear winner on quality. The total list of manual controls on the Canon wins over the Sony. The Sony does have better low light, when both units are in auto mode. I prefer the twin flash cards of the Canon.
I think the deciding factor could be with the housings also. Gates is making a housing for both camera's. But if Gates uses a joystick control for the Canon housing, this will allow for full access to the Canon controls. Which would allow you to have all manual controls and settings available under water. With the Sony you will have more options on housings, for example Light and Motion, Gates, Amphibico, etc. But were not going to know about the housings for at least another 1 - 2 months on both units. I know Light and Motion has a housing available for the Sony, I believe its ready. All other housings aren't available just yet.
The best thing to do is, is find a video shop in your area that carries both models, and go shoot some test footage with both. And see what you like. Take your time, look at as much video footage from both. Do your research read all the reviews. And then see what housings are available.
And don't discount some of the prosumer models either. Like the FX7, FX1, XH-A1, A1U, V1U. Even with a used EX-1 your going to be out of your budget. My final choices were down to the Sony FX-7, Sony V1U and the Canon HF-S10. I decided to stick with the Canon due to size and weight. And I also figured, I can always upgrade later to one of the prosumer models, and sell my Canon set-up or just keep it as a B camera. No matter what take your time, do your research, and no matter what your decision is, chances are you will be happy.
Good Luck! and let us know what you decided. Look forward to seeing some footage from you.
:cool2: