Hi Nicholas,
As you probably know I have setup #1 - though with the viewfinder from setup #2 - so I'd say you're looking at a good pair of systems there.
Things worth noting:
Sea&Sea TTL converter for Canon uses a non-standard, 6-pin Nikonos type bulkhead socket. I have yet to find a way of mounting that on a non-Sea&Sea housing. The Nikon guys get the easy way out, as the S&S TTL converter for Nikon uses the standard 5-pin socket.
The Hugy can be fitted with S-6 socket (for SeaCam flashguns IIRC), but you would need to get a S&S TTL converter adapted to fit in an S-6 socket to use that.
Hugy also now do their own built-in TTL controller for the 5D housing, but that is by it's nature less easy to control underwater than the S&S version.
The Sea&Sea latching mechanism is much quicker to operate than the Hex-key bolt system on the Hugys - we each have a preference.
Hugy can take S&S ports, but not vice versa. Not a big deal, as S&S has some fine ports available, plus plenty of zoom/focus gears. Either way, you may be wanting a 3rd party gear to operate the 100mm USM macro from the body knob. I'll be posting my solution to this one shortly.
The Hugy doesn't provide a thumb paddle for the * button, which is a feature I depend upon with the DX-5D.
Hope that some use,
Martyn