Hi,
I've bought a 5D a month ago, and since then I've been studying the housing that differents brands are proposing for that camera, and I'm still not decided for one housing.
First I have to say that I think that most of the main brands produce excelent products, I mean they have a good building and finish. Some are stronger in some points and others are stronger in other aspects. Ikelite, Subal, Seacam, Hugyfot, Nexus, Aquatica, etc (in my analog days I has an Aquatica F5 housings and it was excelent and very strong), all have good housings.
When I look for a housing one of the first things I check is the ergonomics, that means that I want to reach the main controls easily and with one hand (my right hand) because some times you are not able to use both hands (when it's current) and some times It' better to keep your eye on the viewfinder instead of looking where is the button.
My hand is medium-small, and after checking some of the housings for the 5D, I've seen that, with most of them, I can't reach the 2 main dial comands (front and rear) If I keep my hand on the handle. The only one that allows me to turn main dials and keep shooting with one hand is the Seacam one. I've also concluded that most housing builders do a better job, in terms of ergonomics, when they are producing housings for Nikon cameras.
The only problem with Seacam is the high price.
That's only my point of view.
Jordi