On the other hand, replicas (sometimes called training balls or gliders) are designed to be just like the official match balls but are much cheaper. Their panels are often stitched rather than thermally-bonded and are made of a different material. However, they’re not necessarily less durable than official match balls. So, they’re the recommended option for most players.
If you are unsure of which size to get your child, I will recommend what size I think based off real-world use. The size 3 is good for any child until about first grade or second grade, which is when a child should move into a size 4. The size 4 should last until they get to middle school (around 6th or 7th grade), and then they would move into the adult official size 5.