You will found several comparisons, but all are almost biased by the point of view.
Comparing Hyper-V3 with vSphere 5.1 at features level isn't so interesting... are quite similar.
Comparing on the performance point of view is not simple and may depend by the workload type.
About the complexity I found vSphere simple, but just because I know it well. Hyper-V seems simple for who know well MS technologies.
IMHO for SMB could be similar, but for Enterprise I think that there is a gap and Hyper-V + SCVMM is still a little lower.