Question special

We've heard about two different procedures for performing mitochondrial donation. As I understand it, in a spindle transfer protocol we extract a mother's membrane-surrounded spindle, which contains DNA, and a small amount of cytoplasm from an unfertilized metaphase II oocyte and transfer this into a donor's enucleated oocyte (Tachinaba et al, 2013). This would be followed by artificial insemination and IVF. In pro-nuclear transfer, first the mother's oocyte is artificially inseminated. Then the pronuclei, containing DNA from both the mother and father, is extracted from the zygote and the pronuclei is fused with an enucleated donor's zygote containing healthy mitochondria (Craven et al, 2010). Is there any reason to prefer one procedure over the other? Is one believed to have less risk?Or, is one preferable on ethical grounds? (Also, please correct me if any of those details are inaccurate!)

(Tachinaba et al - doi:10.1038/nature11647)
(Craven et al - doi:10.1038/nature08958)