I have done and enjoyed both tours. It could depend on whether you prefer a touring holiday, or a more relaxed stay in one place. St Lucia has stunning beaches and scenery: Sri Lanka has a very different culture, along with the scenery. There will be lot's of temples, although, unlike Burma, socks can be worn to protect your feet. I'll never foget seeing elephants in the wild, and we very lucky to see a leopard. Then there was Lion Rock and the tea pickers. I could go on and on..... It's a difficult choice, but what ever you decide, you will have a great time