Well, like I said before (http://arclanguage.org/item?id=17988), you're in the wrong place if you're looking for 'futureproof'. The point of arc and its variants isn't to provide any guarantees, but to teach you to fish. If you'd like to be able to build your own lisp while marooned on a deserted island :)
For this purpose, any of these dialects will do. I think I and others here tend to be more well-versed with anarki. Pauan isn't available here anymore, but still easy to contact separately.
