7D for the mag body and overall build, joystick, weather sealing.
i was disappointed when the 70d was announced and did not have the magnesium body. it has a metal core with a polycarbonate shell i think. that doesn't sound as good but after using it for a few months i think it makes no difference. i use some big heavy lenses and was worried that the body would flex under the strain or something. i have not had any problems and i use it in all sorts of conditions. it has gaskets and seals. i have never heard of one breaking in half or anything like that. they make motorcycle helmets and all sorts of things out of polycarbonate and composite materials.
p.s the 7d is bigger and i wish the 70d was the same size for using with the big lenses but for normal size lenses the 70d feels perfect