S-expressions are the nicest syntax. Well, okay, to be fair the real reason is probably because Common Lisp is very mature, well specified, has a lot of useful

S-expressions are the nicest syntax. Well, okay, to be fair the real reason is probably because Common Lisp is very mature, well specified, has a lot of useful libraries (Quicklisp is great), and several implementations can produce very efficient and fast code (about as fast as GC code can be, especially if you make good use of facilities like dynamic-extent).