One big difference was that many of the kills made by Hill were somewhat questionable. When he shot his elephant, it was done poorly. A PH had shot the elephant it one of the knees on a front leg before Hill sent an arrow into it. The reason was an elephant, due to the weight, can not move if a front leg is broken. So this basically anchored the animal in one place until Hill could dispatch it with an arrow. Hill's lion kills were also questionable since there are rumors that they happened inside fenced areas.
There has never been such an accusation against Fred Bear. Remember, Bear owned an archery company and wanted to prove how effective his bows were and didn't do anything to detract from that. Hill was basically an entertainer and wasn't bound by such guidelines.
However, in my book Arthur Young and Saxton Pope pass both these guys up. They hunted the world and took all kinds of game before either Hill or Bear. That's way the record book for bow kills is named after them.