Well, they are of different age and the pictures were taken in different light (therefore the colour difference). But here is the major difference:
The little Lion on the left lives with his family (The North Pride) at Thanda Private Game Reserve in South Africa. The small one on the right lives with his family at the Zoo in Basel, Switzerland. The one lives in the wild with all its dangerous and its beauty, the other one lives in captivity, at full board and with a health care plan 🙂
Congratulations to Peter Mettler, who got the correct answer!
… and now the bonus question, what is so special about this one?