I'll stand by my statement. I don't think any point-and-shoot camera can stand up to a DSLR.
Any point and shoot versus "any" DSLR? I will be happy to take that bet.
There are so many plus and minus issues between the two...don't see how anyone can make a sweeping statement like that.
If you are talking a Sony A900 or a Canon 5D and the issue is resolution.. absolutely.. but then they beat almost all the DSLR's out there.
If we are talking a Nikon D60 versus a G10 at ISO 80, the G10 is far better.
If we are depth of field... and you want more... the G10 is far better... if you want less, a DSLR is better.
If you want to do a dome port, wide angle, in crystal clear water..not seen anything that is as good as a dslr...
If you want to go from macro.. really close macro... with zoom, the G10 is way better.
If you want the least shutter lag...DSLR (although there is a way around that with the G10).
As to why spend all the money for twin strobes...and then buy a lowly G10... well, they can take great images.. and there is something everyone should know about underwater housings... there are two kinds.. those that have leaked and those that will leak. Strobe leaks are no big deal ... cameral leaks are. I can honestly say that when the day comes that the G10 dies underwater.. I will miss it, but then go get another. I've done the SLR route.. and that leak really, really hurts.
I print a lot of my images, usually in 13 x 19...and resolution with a G10 is amazing... assuming you shoot in ISO 80 or 100.
This image is down sized to 1024 x 768...with two YS110's...not cropped... had I taken it with a DSLR, I would be hard pressed to understand how it would be clearer and sharper or anythinger.
The conditions were at about 100 ft, vis around 20 ft... a light was needed if you wanted to see under any ledge, as it was pretty dark.