Different cameras have different meters, different metering modes, etc. So it's not surprising to get different readings. Make sure the subject on both is exactly the same though.
If you really want to compare the 2 meters, best way is to use a 18% grey card and fill the frame on both cameras. Using this method, I obtained the same readings on a Nikon F100, Canon D30, Nikon Coolpix 950 and a Minolta Flash Meter IV (incident light meter/flash meter).