They both involve a wolf and a sheep/lamb/goat (whatever you want to call it) spending time together, just in different ways. In Chirin no Suzu, the sheep is the wolf's apprentice and eventually his friend. In Arashi, the wolf and sheep are best friends. In both movies you wonder how such relationships may conquer the odds. They both have a lamb-goat who's mother was killed by a wolf. Both movies may seem for children, but in fact, they are a bit dark (for a mature child maybe?). These movies are perfect for adults or teens with an inner child.
A lamb whose mother is killed by a wolf later befriends a wolf. Both revolve around their relationships.
However, Arashi no Yoru ni is much more light-hearted and family-friendly than Chirin no Suzu. Chirin is darker and more mature, not really one for the kiddies.
Both deal with relationships not accepted by society as
portrayed by animals. The main characters in each are ostracized at some point by society and must deal with the realities of their relationship.
In Arashi it's a friendship between a wolf and a sheep
and in There She Is it's between a rabbit and a cat.
Both shows a heartwarming relationship of two different species. Deai-rabbit and frog. Arashi no Yoru Ni-Wolf and Sheep. Differences doesn't matter in order to get along. You'll like both if you like unusual pairing of animals.
Both stories are meant particularly for children, and they both revolve around animals and their way of living. If you liked Jungle Emperor Leo, then you'll probably find Arashi no Yoru ni to be even better.