Googling the issue I found a lot of claims that pulling is more efficient but universally I found no attribution of proof, only repeating what they'd heard someone else say. I did find one site for engineers apparently where the claim is just the opposite. <CLICK>

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.