Duh ya, but what does shooting in Medium do, throw away some info, crop the Image/Sensor, or just process it differently?
42-75MBs seems low to me for a D800 RAW image. My Large Fine JPEGs often go over 30.
These are usually to large to email. Using MED size for D800 and Large Fine Best quality settings for the D600 net about 9-15 MegaBytes that are much easier to deal with. Of course, if I were selling Art Objects instead of Memories, I would have to shoot RAW and do a whole lot more post processing.