There have been some great points made here and i thought i would just throw my own in as i am in exactly the same position as you.. Been using a G10 for a while but it pangs to see my 5D MkII sitting there, calling to me! Personally i have made a decision to go for the Aquatica housing and a few reasons for this one..
Firstly, i am a tech diver and it comes rated to 90m and for an extra £35 you can get the upgrade for 130m. Apart from the hugyfot that is rated to 100m all the others are around 60-70m, and when you look at the cost of the seacam etc i think it is bonkers.
Secondly.. i also do underwater videography, and like the guy from backscatter mentioned it seems to be the best thought out for this by ways of the hydrophone etc..
Thirdly, when it comes to price i think that the aquatica is by far the best priced option (although cheaper would always be much appreciated!!
) ok, so it is over $1000 more expensive that the ike but look at what you get for that.
People always go on that with ike's you can see if you camera floods. Well.. it is too bloody late by then anyway, so this option in my mind doesn't count for anything when you look at the leak detectors you can get for the other systems.
Plus i feel that the aluminium housings are just that much stronger that the ike's. I have seen soooooo many people leave the ike housings in the sun for just a bit too long and then the plastic starts to fog up. People say that ike's are cheaper but if you take in to consideration the number of people that have flood's etc.. and their lifespan i think they work out to be a lot more expensive in many ways. As someone else said, you do get what you pay for and whilst they may appear cheaper at first it is all too easy for them to end up costing you a lot more.
They hugyfot seems to have a good system for checking the seal before you get in the water but i just can't sstretch that far on the budget but think i would stick with aquatica even if i could.
But, bear in mind all this ramblings come from someone that has never owned a Dslr housing before, but from someone that is about to make the plune themselves. I am sure that like everything else it is very much a personal choice, of course backed heavily by how much credit you have available but i just can't quite see how to justify seacam and subal's prices when there is a housing that appears to be just as good if not better available to a lot less.. i.e. the aquatica
Anyways.. let us know which way you go, and personally i would love to know how it turns out for you and how you find which ever housing you go for as i dont quite have enough money yet so i can still change my mind! ho ho..