Who makes the strongest full-frame body?

Are there any opinions to what camera body is the most durable and solidly built?

I’m thinking about moving from one full-frame camera & maker to a different one.

I’m looking at the Canon 5d3, Nikon d800 or the new Sony a99, but needs to be well made!

And if I moved up to the pro Nikon d4 or Canon 1 body would that make it less likely to be damaged  in a drop?