Curved sopranos were more common during the thirties and look like miniature altos. Straight horns typically have better intonation than some of their curved counterparts. The soprano is in the key of B flat, one full octave higher than the tenor. The soprano is a highly enchanting instrument with an etherial sound and an intoxicating feel for the player. Unfortunately, it's also generally accepted as the most difficult saxophone to learn and master, and is not recommended for beginning players.
Intonation is a big issue - it requires an extremely precise embouchure and tons of practice time.
The soprano is most commonly used in jazz and has a limited classical repetoire available. The soprano is, however, a great deal of fun to play. The alto is a medium sized saxophone and is the most commonly played size. Most beginners start with alto due to its comfortable size and shape. The alto is the most recommended horn for those just starting on the saxophone.