"Comparing" is a tad harch, its more like an apples to oranges and Klingons to Jedi thing:
 
"This article compares all the affordable weather-sealed DSLR cameras in production. These DSLRs are the Canon EOS 7D, the Nikon D300S, the Olympus E-3, the Pentax K-7, the Pentax K20D and the Pentax K200D. The definition of weather-sealed varies between models but does not mean waterproof, so all DSLRs

require a special housing for under-water use"
 
Link