Efficiency and portability are usually conflicting objectives for cluster-based network servers that distribute the clients' requests across the cluster based on the actual content requested. Our work is based on the observation that this efficiency vs. portability tradeoff has not been discussed before in the literature. To fill this gap, in this paper we study this tradeoff in the context of an interesting class of content-based network servers, the locality-conscious servers, using modeling and experimentation. Our analytical model gauges the potential performance benefits of portable and non-portable locality-conscious request distribution with respect to a traditional, locality-oblivious server, as a function of multiple parameters. Based on our experience with the model, we design and evaluate a portable, locality-conscious server. Experiments with our server, a non-portable server, and a traditional server validate and confirm our modeling results under several real workloads. Based on our modeling and experimental results, our main conclusion is that portability should be promoted in cluster-based network servers with low processor overhead communication, given its relatively low cost (<= 15%) in terms of efficiency. For clusters with high processor overhead communication, efficiency should be the overriding concern, as the cost of portability can be very high (as high as 106% on 32 nodes). We also conclude that user-level communication can be useful even for non-scientific applications such as network servers.