Honestly, I don't think either breed would be a good choice. Akitas can be pretty aggressive towards other animals. In fact, the breed standard says they may be intolerant of other dogs, particularly of the same sex.
Temperament: Alert and responsive, dignified and courageous. Akitas may be intolerant of other dogs, particularly of the same sex.
Shibas aren't very big- only about 25 pounds. The standard says they can be aggressive towards other dogs, too.
Temperament:A spirited boldness, a good nature, and an unaffected forthrightness, which together yield dignity and natural beauty. The Shiba has an independent nature and can be reserved toward strangers but is loyal and affectionate to those who earn his respect. At times aggressive toward other dogs, the Shiba is always under the control of his handler. Any aggression toward handler or judge or any overt shyness must be severely penalized.