Leather and synthetic boots are both available.
There are advantages with each and you should make your own judgement by trying both.
Leather moulds itself to the shape of your feet but can stretch out of shape in wet conditions.
Synthetic boots are often lighter and less expensive.
Try and find soft "uppers" that give you the best control of a ball - you may even find that a boot that combines leather and synthetics is best for you.
The position of the laces can vary on boots.
Some manufacturers offer boots which have the laces moved slightly down the outside of the boot, the aim being that it creates a larger and cleaner surface area on the top of the boot to control and strike the ball.