Unwrap the GS and the u'll hav a winner in every other horological aspects; case, movement/accuracy, bracelets confort, crown details and of course polish/shine. Cartier will only wins on the public/brand recognition part. But its juz my opinion...
Btw, i own a GS snowflake and coincidentally looking for a Cartier Santos. Hmmmm, maybe its a sign i should pull the trigger..
