A: Butyl bladders are an excellent choice for the interior of soccer balls because they create an airtight seal in the inner compartment. This helps greatly with air retention. Even better, you will not have to keep inflating soccer balls that contain a butyl bladder for the fact that they hold air much longer than soccer balls that don’t have a bladder made from butyl rubber.
A Futsal ball is basically an indoor soccer ball used for playing 'Futsal', a term literally meaning 'indoor football'. Futsal is a kind of soccer played on a basketball-sized court using a smaller, heavier, less bouncy ball, and demands many of the same skills as outdoor soccer. Size-wise, FIFA-approved futsal balls are just shy of 25 inches in circumference, slightly smaller than a Size 4 soccer ball. The ball is created with less bounce to facilitate indoor play.
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. https://www.youtube.com/watch?v=j2Xn84L3Kcs