Not to think that the Silk Road was not significant, because it was, but the voyage across the sea and desert just seem so challenging for this time period.
The sea roads showed a significant growth in trades, being able to move vast amounts of supplies. This differed from the Silk Road trading, which limited to a smaller quantity of goods, whereas the ships allowed for larger amounts of cargo. Aside form the amount of cargo, the evolution of shipbuilding was just beginning, so it is astounding that people actually even survived a trip, let alone stimulating wealth through trade. This allowed people to travel to various countries without having to stagnate their trade within one country.
In reference to the Sand roads, what was striking to me, would have to be huge amount of camels and caravans that traveled across the desert. Not only was this just any average dessert, this was the SAHARA. The travelers had to factor the heat of the desert, thus forcing them to travel at night. Also, the time period it took, taking months at a time to travel, requires a good amount of patience before an actual transaction is even made.