Of those 3, I would highly recommend the NACRA 5.7. Boardless *and* boomless, it has fewer controls, and is still in production (as NACRA 570).
As another poster pointed out, there is also a G-cat 5.7m, which is also board-less. It has a boom, but, it has a front crossbeam, to which I have seen folks add a forward trampoline.