Adult stem-cell research is nothing new. It has been going on for decades, and in fact has proven helpful in treating various diseases. In the process of this research, nobody has to be killed in order to obtain the stem cells.
Embryonic stem cell research, on the other hand, only began in 1998, and does involve killing a new human life in order to obtain the cells. The number of diseases that have been successfully treated with embryonic stem cells is zero. They have shown no medical benefit. And even if they did, such activity is immoral. The end does not justify the means.
Adult stem cells have treated various forms of leukemia, sickle cell disease, anemia, and carcinoma. Embryonic stem cells have succeeded in nothing.