  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.
