LayerVault is a great tool if you want to keep your design files version controlled and nicely organized, which is the primary function. They have also introduced a handoff feature (http://layervault.tumblr.com/post/82302518939/introducing-as...) that is somewhat closer to Avocode. But Avocode aims to be your tool of choice when it comes to designer->developer interaction and VICE VERSA. Many services often forget those developers who must code the same parts over and over again.