Good fight. Animal will, unquestionabally have better control over animals. He's able to be physically superior in every way, too. I don't know is aqua still has the magic hook, he so he wins. Is not, he loses.
Even without alien powers Buddy should easily beat Arthur.
By taking on the power of a bacteria he can outnumber Arthir 1000/1.
By taking onnthe power of a kracken he is stronger and more durable.
By taking on the relative time rate of a fly he statues Arthur.
By taking on the power of Bwanna beast he has superior TP (though given he controls ALL animals he already has an edge there)
By taking on the power of an earth worm he can regrow completley severed body parts and regenerate from anything.