The benefits of cloning human embryo are few if any. But one benefit is
to try and help those couples who are having trouble having their own
babies. But yet there is also the point you make about killing one of
the twins, if two embryos are implanted. I guess it is not up to us to
make the decision of how many implantations of embryos there are going
to be in this lifetime.
In the next few months or even years we will be seeing many changes in
the scientific research and new advances in the study of embryo cloning,
I guess we'll just have to wait until then to see what the benefits are.