First DSLR camera

I have an Olympus C-8080 in a PT-023 housing (yes, the port is held on with duct tape and I get a lot of comments but it has made 68 dives that way), heinrich adaptor, and Nikonos 105 strobe that I have been using for a little over a year (70 dives). Previous to this rig I used a Nikonos V for quite a few years. I have decided to upgrade to a DSLR. I was seriously looking at the Canon 400D when the Olympus E-410 came out and started getting a lot of good press and I have come to like the 4/3 picture on my present Olympus. Both are 10 megapixels but the 400D chip is larger. Is this significant with respect to picture quality? I would be interested in hearing what people think are the +'s and -'s of each camera with respect to underwater photos. I plan on also getting a Inon z-240 or S&S 110 strobe and will probably get another heinrich adaptor. Thanks,