that is very kind of you, thank you, same back at you.
firstly, i reject that either of these is critical to a marriage, or that they are mutually exclusive.
however, i would actually say that sexual fulfillment is more important. why? sex creates children, and sexually fulfilled people are likely to be happier people, and happier people tend to be better parents, citizens, etc. the earth is overpopulated as it is, and as people tend to become wealthier and more educated, they tend to have fewer children. quality over quantity, imho.
as another thought: we all agree that children do best in stable households. would it not be an unambiguous positive if there were more gay people, unable to have children of their own, who are in stable, committed, protected marriages who might then be more inclined to adopt children in need of homes.
in fact, don't we all benefit when adults -- especially, dare i say it, adult males -- have an investment in their own stability?
(this is not to say, however, that one can't be perfectly happy and productive as a single adult, or that one can't be the same without children -- there are many, many ways to live, and there are many for whom societal conventions aren't a good fit).