I feel greatly sorry for you. No matter how much you asked for it yourself it is always a sad thing you gear starts malfunctioning.
If it's okay with the OP I'dd like to ask you all for some advice in what to do in my own situation. I have a 5D Mark III which is currently in for repair by water damage. Canon has opened up the camera and found several spots where water has damaged multiple parts of the camera.. My problem however is not whether or not water has damaged my camera as canon have already sent me pictures of the internals of my camera. My problem is that this damage has happened over night where i was sleeping in a tent. The camera what functioning perfect when i went to sleep and not at all when i woke again. Therefor i suspect the camera to be damaged only by moisture and condensation, which i find to be less than satisfying.. Another thing to add is that my 5D Mark II was right next to it and it suffered no malfunctions.
I am very disappointed with this. And of course the bill that followed, which right now I'm refusing to pay...
I live in Denmark, if that is of interest for anyone. In Denmark the price for a 5D mark III is just about 4000$ and the cost of the repair is 2800$... Almost 3/4 of the price of a new one...
So if anyone can provide some help in any way i would be more than thankful also pictures like the one of the 6D's sealing would be nice to have. Thank you all in advance!
this link, posted twice already, states that the 5DIII sealing is better than the 5D II.
I presume there may be other tech reports on that site, which have other little tidbits.
As to your particular case, it's rather difficult to judge what has been going on. Even though one camera is dead, and the other not, maybe even small differences in location may have done it, i.e. one underneath the other, liquid going down, etc. Also, did it rain during the night, was the tent waterproof, i.e. a little water dripping here or there exactly on the one camera, but not the other, while you were sleeping.
It didn't rain at all. And just for the sake of it, the tent was waterproof anyway. Though I get your point in regards of small differences in location might have done the trick, i still don't understand as they were just beside each other.
As to the part of the 6D pictures I wasn't looking for the 6D pictures or links for them, but rather similar pictures of the 5D mark III