Supersymmetric Grand Unification: the quest for the theory

With the advent of neutrino masses, it has become more and more acknowledged that SO(10) is a more suitable theory than SU(5): it leads naturally to small neutrino masses via the see-saw mechanism, it has a simpler and more predictive Yukawa sector. There is however a rather strong disagreement on what the minimal consistent SO(10) theory is, i.e. what the Higgs sector is. The issue is particularly sensitive in the context of low-energy supersymmetry.