Conventional wisdom is that undifferentiated cells will be easier to remodel and reprogram during SCNT because their epigenetic marks are closer to the totipotent state.
When the ability to be reprogrammed was tested, SCNT embryos derived from earlier blastomeres had a higher ability to develop to term; also, as mentioned earlier, the first pig cloned by NT was produced from a blastomere.
Successful cloning has been reported in mice using ES cells, and has shown higher post implantation development compared to SCNT-derived embryos. However, this conventional wisdom has been called into question, as there is also evidence that the state of differentiation may not be the determining factor.