The simple fact is that the bigger dogs are more expensive to treat than the smaller ones. Though the bigger bigger-sized dogs may be equally as cute and cute, you would require a much larger space for your dog.
Bigger dogs would also require you to have more space to get them run around in. In case you've got a large enough garden, it would be better for you to leave the dogs on a large piece of land. A great stretch of tranquil lawn would suffice.