You have a heat pump. You're pumping heat from the interior of the fridge to the exterior of the fridge.
If you're choosing the part of the fridge's exterior that gets the heat, then If it's winter, and you want to heat the house, it will be beneficial to vent the fridge to the kitchen. If it's summer, and you want to cool the house, it will be beneficial to vent the fridge to the outside.