Koh Samui is more of beaches, waters and water sports. It’s famous for picturesque views, sunrise and sunset views and few lovely islands nearby. Koh pangan is called gem of Thailand which has lovely weather, great party culture, scuba, best sea food and jaw dropping trek views. Koh tao is called as secluded paradise hamlet, meaning turtle island. Beauty prevails both external and inside the waters of this island. An ideal place to view best underwater sea life. My choice would be Koh Phangan and Koh tao.