Hamsters are very social pets. While many small pets do more to tolerate your presence, hamsters have a great desire to be with their human companions. A full grown rat is big enough to be easy to handle, but small enough for almost any living situation. Hamsters can be free ranged in the house so long as everything is adequately 'rat proofed', they can be litter trained and can learn tricks. A well trained rat can ride on your shoulder. While hamsters are social animals, it is not entirely uncommon to find one that doesn't appreciate cage-mates, which can lead to fighting. Hamsters can make very good pets for families as they are very disinclined to bite.
Children need to be observed with hamsters to make sure they do not pick up or restrain a rat by it's tail as it can very easily become injured. Some hamsters will scent mark by leaving a drop of urine as they walk, although this depends on the rat. They need plenty of toys and human interaction or they can become bored and depressed. Many hamsters will develop respiratory problems, especially if their litter is not changed daily, and tumors are not uncommon. They usually live for about 2 years at most.
Chinchillas live for a long time, typically about fifteen years, which is great if you want a long time companion. They can be kept alone and also do well in same sex pairs. They make very interesting pets, and a properly chinchilla proofed room provides a great playground. Chinchillas are also odorless pets.
Chinchillas are very quick and require a gentle touch and generally like to be on the move rather than being held. They require large living spaces and cooler temperatures at about below 82 degrees or they risk getting heat stroke. Because they don't appreciate being held tightly or for too long, many chinchillas don’t often make good pets for children. Despite being odorless pets, chinchillas can make a mess with their hay and dust bath.