It's not the camera it's the lens(s). Oh yeah, also 4-6 frames a sec RAW, seeing actual focus, battery life, and on and on.
I shot a couple of 10MP Fuji P&S for 3 years and they were fine. But nothing compared to my D80 with a 60mm macro. And I'm sure the Canon's are just as nice.
I'm blind as a bat, middle-aged and wear contacts UW. I can see the viewfinder in my D80 just fine. Can I see all the edges at one time? Sometimes, but it really doesn't matter. I can shoot 4 frames in the time I could shoot one with a P&S, because I have a frame buffer.
Size and weight is bigger, but I find that my
Fantasea FD80 housing isn't that much more to swim than my old Ike Fuji system because it's much less negative.
Yes, the new P&S, like the Nikon P5100, are awesome for $399 list. Throw it in a small
Fantasea FP5000 for $209 and off you go.
If you want instant, repeatable shooting, much greater versatility, sharp as a tack shots and much more, get a DSLR.It really comes down to your budget.
BTW, the D300, etc with live view have not hit the streets yet it may be several months before housings and so forth are out. Also yet out is quite how well you can focus with LiveView.
Jack