Internet traffic is highly dynamic and difficult to predict in current network scenarios, which enormously complicates network management and resources optimization. To address this uncertainty in a robust and efficient way, two almost antagonist Traffic Engineering (TE) techniques have been proposed in the last years: Robust Routing and Dynamic Load-Balancing. Robust Routing (RR) copes with traffic uncertainty in an off-line preemptive fashion, computing a single static routing configuration that is optimized for traffic variations within some predefined uncertainty set. On the other hand, Dynamic Load-Balancing (DLB) balances traffic among multiple paths in an on-line reactive fashion, adapting to traffic variations in order to optimize a certain congestion function. In this article we present the first comparative study between these two alternative methods. We are particularly interested in the performance loss of RR with respect to DLB, and on the response of DLB when faced with abrupt changes. This study brings insight into several RR and DLB algorithms, evaluating their virtues and shortcomings, which allows us to introduce new mechanisms that improve previous proposals. Keywords: Traffic Uncertainty, Traffic Management, Robust Optimization, Robust Routing, Dynamic Load-Balancing