A few different reasons to want to upgrade to the DSLR.
First, to be able to shoot more than 1 picture in Raw mode every 10 seconds-like that 5060 set up you posted.
Second, shutter lag- it's worse than jet lag.
Third, sharper images that come from a larger processor- 10 mega pixels in a sub compact is not the same as 10 mega pixels in a DSLR.
Fourth, better low light capabilities with less picture noise.
Fifth, No hassle, or at least less hassle, split level shots. Too much of a pain working with any of the add on lenses and dealing with water filling in and leaking back out.
I just got back from another camera shop, where the clerk next to nothing, and took a look at the E-410. The thing is tiny and has the live view back panel- which the clerk assured me it did not until I showed him it did. This puts it up a notch, for me, from the D-40 and the XTI.
I'd like to find a better picture of the housing, but judging from the size of the camera I'm betting on the fact that the whole system would be no larger than my old 5050 setup.
I've been shooting still for a long time and there's just nothing that can capture a moment like a well composed still. Video is great for movement- like swimming with dolphins, but that shipwreck isn't going to go anywhere and you can grasp more of it's mystery with a photo than a video clip. Different mediums for different purposes.
A tech diving buddy of mine passed away last year- not from diving, but rather a mix of high blood pressure and age. He was at the forefront of trimix diving and video work in this area long before anyone else came along. His advice to me over 10 years ago was this; the two happiest days in the life of a videographer are the days he buys his setup and the day he sells it. He said that when he had a bunch of unedited footage sitting around he always felt guilty for not working on it. Even when he had it finished he knew there was always something more he could do. I've only made one, goofy, little video for you-tube so far and already there are a dozen things I'd do differently. I can imagine it only gets worse when your dealing with more of it for clients and other presentations.rofl
Jon