Thank you for your interest in Yamaha guitars. The CGS103AII and CS40 II are very similar guitars, made to the same specification (with spruce top and meranti back and sides with a nato neck) but in different guitar workshops (which allows us to keep up with the high demand for our three-quarter size classical guitars across the world). The CS40 II tends to be the more popular in the European market, but essentially, both are great guitars.
However, for beginners aged around 7 and up, we'd strongly advise starting on a full-size classical guitar, such as the C40 II (available by itself in natural wood or black finish, or as part of a starter pack) - see the links below.
At ten years old, playing a full size classical is manageable and ensures the player becomes accustomed to playing a full size instrument.