High quality basketballs are made of genuine leather or composite leather (cheap balls are made of rubber). Balls that are made of genuine leather are generally considered to be the best ones and are used in the NBA and WNBA. They are also the most expensive type of balls.
Synthetic or composite leather is an artificial type of material that feels like leather but is cheaper to produce and the balls therefore are not as expensive as the leather balls. The materials are also more versatile and can be used both indoors and outdoors, although outdoor play wears the ball down quicker so we would not recommend it for the better composite balls.
The feel of a genuine leather basketball is completely different to the composite balls. NBA tried in 2006 to replace the leather ball with a composite ball, as the composite has a few advantages such as it does not need a break-in period and thus achieves consistency from ball to ball making the game more about how you play and not the material used. This is because genuine leather match balls used in top level games have been meticulously prepared through a 90-day process to become fully match ready. This also indicates that there may be differences between balls. The NBA, however, needed to reinstate the genuine leather balls in mid-season due to complaints from the players.
When you buy a genuine leather ball, such as the Molten GL7X or Spalding NBA Official basketball, you need to be aware that you need to break in the ball before you get that superior ball you paid for. If you do not want to go through that trouble, a high-quality composite ball such as the Molten GG7X is better for you. It is good enough to be used throughout the Euroleague so you will not be disappointed.