Major is larger, greedier and more dominant, therefore he stands over Del until she drops her bone. He then drops his larger bone and grabs her smaller one, thinking he'll have two. Whereupon Del snatches up Major's larger bone and takes it out onto the grass where she guards it zealously and crunches on it for an hour or so.
Their evening meal is different. Del maintains total control over her plate and its contents and for whatever reason, Major respects this. Admittedly, we've never allowed Major to take Del's dinner so probably this is more a matter of training. As time goes by, it will be interesting to see if Del can maintain her position of top dog against Major's 60 kg body and dominant nature. I've always found dog psychology to be a fascinating subject and our two shepherds provide plenty of raw material for study, observation and amusement.